UNIVERSITY  OF  CALIFORNIA 
AT  LOS  ANGELES 


Examination  of  Portland  Cement 


THE 

Chemical  and  Physical 
Examination 


Portland  Cement 


RICHARD  K.  MEADE,  B.S., 

Instructor  in  Chemistry  in  Lafayette  College 


EASTON,  PA.: 

THE  CHEMICAL  PUBLISHING  COMPANY. 
1901. 


COPYRIGHT,  1901,  BY  EDWARD  HART. 


TT 


PREFACE 

^        In  the  preparation  of  this  little  manual,  the  author  has 

o»    drawn  largely  for  advice  upon  his  friends  and  others  en- 

^    gaged  in  the  cement  industry  who  were  kind  enough  to 

give  him  help,  and  it  is  to  thank  these  that  he  has  pre- 

fixed this  note.  Aside  from  this,  it  may  not  be  amiss  to  say 

here  that  this  book  is  the  outcome  of  the  author's  interest 

^   in  the  rapidly  growing  Portland  cement  industry  in  Amer- 

^    ica.     The  methods  both  of  chemical  analysis  and  physical 

examination  have  been  explained  with,  what  may  seem  to 

the  experienced  chemist,  useless  detail,  but  it  must  be  re- 

i    membered  that  many  of  the  cement  manufacturing  com- 

\.    panics   are   employing   young   men   fresh  from  technical 

^i    schools,    whose  college   training  may   be  excellent,  but 

>-  whose  laboratory  experience  upon  work  of  this  kind  is 

,0   usually  limited  to  a  few  analyses.     Probably  the  greater 

"    number  of  young  cement  chemists  are  required  to  make 

^  ,    physical  tests  without  having  had  any  training  whatever 

in  the  subject.     It  is  for  these,  as  well  as  the  young  en- 

^    gineer  and  the  student  of  chemistry  and  engineering,  that 

the  notes  and  explanations  have  been  added  to  the  methods. 

The  author  wishes  to  acknowledge  his  indebtedness  to 

Prof.  J.  Madison  Porter,  C.E.,  of  Lafayette  College,  and 

to  Dr.  P.  W.  Shimer,  of  Easton,  Pa.,  for  their  kind  help. 

Professor  Porter  read  the  section  upon  the  physical  test- 

ing of  cement  and  added  much  to  its  value  by  his  sug- 

gestions for  its  improvement.     Others  who  have  kindly 

*M\ 


iv  PREFACE 

aided  the  author  are  :  Messrs.  Andreas  Lundteigen,  chem- 
ist, Western  Portland  Cement  Co.,  Yankton,  S.  D.;  Julian 
O.  Hargrove,  assistant  inspector  of  asphalt  and  cements, 
District  of  Columbia ;  Thos.  A.  Hicks,  chemist,  Art  Port- 
land Cement  Co.,  Sandusky,  O.;  S.  B.  Newberry,  manager 
Sandusky  Portland  Cement  Co.,  O.;  J.  G.  Bergquist,  su- 
perintendent cement  department,  Illinois  Steel  Co.,  Chi- 
cago ;  J.  Dunraven  Young,  analytical  chemist,  Chicago  ; 
Willett  C.  Pierson,  chemist,  Glens  Falls  Portland  Cement 
Co.,  N.  Y.;  and  A.  C.  Ferguson,  C.E.,  St.  Louis  Water 
Works  Department. 

LAFAYETTE  COLLEGE,  EASTON,  PA.,  June,  1901. 


CONTENTS 


INTRODUCTION. 

The  nature  and  composition  of  Portland  cement  and 

current  theories  of  its  hardening,  1-14 

Definition,  i  ;  analysis  of  various  Portland  ce- 
men'.s,  2  ;  composition  of  cement,  3  ;  theory  of 
the  hardening  of  cement,  4  ;  hydraulic  index, 
5  ;  Messrs.  Newberrys'  theories,  6  ;  Newberry's 
formula,  7  ;  substances  found  in  cement,  7  ; 
lime,  8  ;  alumina,  10  ;  ferric  oxide,  10  ;  mag- 
nesia, ii  ;  alkalies,  12;  sulfur,  12:  carbon 
dioxid,  13  ;  analysis  of  natural  cements,  14. 

ANALYTICAL  METHODS. 

THE  ANALYSIS  OF  CEMENT,  15-82 

Preparation  of  the  sample,  -  -     15-20 

Sampling,  15  ;  grinding,  16  ;  drying,  17. 
Determination  of  silica,  ferric  oxid,  and  alumina,  lime, 
and  magnesia,  20-40 

Notes  on  the  decomposition  of  cement,  20  ;  by 
ignition  of  the  sample  with  sodium  carbonate, 
23  ;  by  solution  of  the  sample  in  HC1  and  fu- 
sion of  the  insoluble  residue  with  Na2CO3,  26  ; 
by  fusion  of  the  sample  itself  with  sodium  car- 
bonate, 28  ;  rapid  method  by  simple  solution 
in  dilute  hydrochloric  acid,  30  ;  notes,  33. 
Volumetric  determination  of  calcium,  -  40-42 

Volumetric  determination  of  magnesium,  42-48 

Rapid  determination  of  silica  and  lime,        -  48 


vi  CONTENTS 

Determination  of  ferric  oxid,      -  49~59 

By  titration  with  potassium  bichromate,  49  ;  by 

titration  with  potassium  permanganate,  53. 

Determination  of  sulfuric  acid,        -  -     59~6I 

By  solution  in  HC1,  59  ;  by  fusion  with  Na^CO., 

and  KNO3l  60  ;  notes,  61. 

Determination  of  sulfur  present  as  calcium  sulfid,  61-64 

Determination  of  carbon  dioxid  and  combined  water,      64-73 

Determination  of  carbon  dioxid  alone       -  73-?8 

By  ignition,  73  ;  evolution  with  HC1,  74  ;  rapid 

determination,  76. 

Determination  of  loss  on  ignition,      -  -  78 

Determination  of  alkalies,        -  78-81 

J.  Lawrence    Smith's    method,  78;    Stillman's 

method,  80. 

ANALYSIS  OF  CEMENT  MIXTURES,  SLURRY,  ETC.,     -     82-104 
Rapid  methods  for  checking  the  percentage  of  calcium 

carbonate  in  cement  mixtures,  83-99 

By  standard  acid  and  alkali,  83  ;  by  Scheibler's 

calcimeter,  94. 

Complete  analysis  of  cement  mixture  or  slurry,  -   99-104 

By  fusion  with  sodium  carbonate,  99  ;  by  igni- 
tion with  sodium  carbonate,  103. 

ANALYSIS  OF  LIMESTONE  -         105-112 

Determination  of  silica,  ferric  oxid,  and  alumina,  lime 
and  magnesia,    -  105-1 1 1 

By  ignition  of  the  sample  with  sodium  carbonate, 

105  ;  by  solution  in  hydrochloric  acid,  109. 
Determination  of  organic  matter,  insoluble  silicious 

matter,  ferric  oxid  and  alumina,  lime  and  magnesia  111-112 
Determination  of  alkalies,  sulfuric  acid,  carbon  dioxid, 
combined  water,  and  loss  on  ignition,   -  -  112 


CONTENTS  vii 

ANALYSIS  OF  CLAY,  113 
Determination  of  silica,  ferric  oxid,  alumina,  lime 

and  magnesia,    -                                                     -  113-117 

Determination  of  free,  hydrated,  and  combined  silica,  1 1 8-1 20 

Determination  of  water  combination,  120-121 

Determination  of  sulfur  and  iron  pyrites,  121 

PHYSICAL  METHODS. 

Specific  gravity,     -  122-125 

With  L,e  Chatelier's  apparatus,  122  ;  with  the 
Schumann-Candlot  apparatus,  123  ;  with  the 
specific  gravity  bottle,  124. 

Fineness,        -  -          125-126 

Importance  of  fineness,  125  ;  method  of  making 

the  test,  126. 

Setting  properties,  126-131 

Value  of  the  test,  126 ;  method  of  making  the 
test,  128;  German  method,  128;  with  the  Vicat 
needle,  129. 

Tensile  strength,  -          131-154 

Briquettes,  131 ;  molds,  133  ;  sand,  134  ;  making 
the  briquettes,  134  ;  mixing  the  mortar,  136 ; 
hardening  the  briquettes,  137  ;  clips,  138  ;  ce- 
ment testing  machines,  140  ;  lack  of  uniformity 
in  tensile  tests,  146;  jig  mixer,  147 ;  Faija 
mixer,  148 ;  Bohme  hammer,  149 ;  Jameson 
briquette  machine,  150 ;  Porter-Olsen  testing 
machine,  153. 

Soundness,  155-165 

Importance  of  the  test,  155  ;  cold  test,  156 ;  ac- 
celerated tests,  158  ;  Faija's  test,  158  ;  Maclay's 
test,  160 ;  kiln  test,  161  ;  boiling  test,  163  ; 


viii  CONTENTS 

calcium  chlorid  test,    163;  Bauschinger's  cali- 
pers, 164.    ' 

DETECTION  OF  ADULTERATION  IN  PORTLAND 

CEMENT. 

Detection  of  adulteration  in  Portland  cement,         -          166-173 
Tests   of  Drs.    R.  and   W.    Fresenius,    166 ;    Le 
Chatelier's  test,  170  ;  Microscopic  test,  172. 

APPENDIX. 

Table  of  the  atomic  weights  of  the  more  important  ele- 
ments, -  174 
Table  of  factors,  175 
Table  for  converting  CaSO4  to  CaO,  -  176 
Table  for  converting  Mg.2P2O7  to  MgO,  -  177 
Specific  gravities  of  nitric  acid,  -  178 


INTRODUCTION 


The  Nature  and  Composition  of  Portland  Cement 
and  Current  Theories  of  its  Hardening 

Portland  cement  is  a  product  resulting  from  the  heating  to 
incipient  fusion  of  a  mechanical  mixture  of  limestone  and 

clay,  or  similar  materials  containing  silica,  lime 
Definition.  f 

and  alumina,  and  then  grinding  finely  the  re- 
sulting clinker.1  When  the  fine  powder  is  mixed  with 
water  chemical  action  takes  place,  and  a  hard  mass  is 
formed.  The  change  undergone  by  the  cement  mortar  in 
passing  from  the  plastic  to  the  solid  state  is  termed  "set- 
ting." This  usually  requires  but  a  few  hours  at  most. 
On  completion  of  the  set  a  gradual  increase  in  cohesive 
strength  is  experienced  by  the  mass  for  some  time,  and 
the  cement  is  said  to  "harden."  Cements  usually  re- 
quire from  six  months  to  a  year  to  gain  their  full 
strength.  Cement  differs  from  lime  in  that  it  hardens  while 
wet  and  does  not  depend  upon  the  carbon  dioxid  of  the  air 
for  its  hardening.  It  is  very  insoluble  in  water  and  is 
adapted  to  use  in  moist  places  or  under  water  where  lime 
mortar  would  be  useless.  Below  is  a  table  showing  the 
analysis  of  various  Portland  cements. 

1  German  standard  rules. 


INTRODUCTION 
ANALYSIS  OF  VARIOUS  PORTLAND  CEMENTS 


No. 

Si02 

A1203 

Fe203 

C&O 

MgO 

Na2O 
K20 

S03 

CO*        H.O 

I 

23.30 

5.85 

4.65 

60.90 

0.90 

0.30 

2-43 

1.40 

2 

22.04 

7-35 

4.14 

61.94 

0.91 

0-59 

1.38 

1.65 

3 

19-55 

10.65 

3-30 

59-55 

2.41 

0.88 

2.08 

1.40 

4 

27.74 

7-74 

3-70 

56.68 

0-57 

0.63 

1.66* 

6.28 

5 

27.18 

8.85 



59-50 

I.4I 



0.99 

6 

25.60 

6.13 

3-47 

60.19 

0.70 



r.13 

'2.70 

7 

22.20 

6.72 

2.28 

67-31 

0-95 

0.26 

0.40 

8 

26.OO 

6.65 

2-75 

61.60 

1.08 



0.84 

1.  10 

9 

22.63 

7.06 

2.42 

60.81 

2.89 

2.83 

0.47 

0.33    .... 

10 

22.85 

5-51 

2.76 

65-59 

1.24 

0.92 

1.69 

__ 

2O    8O 

7    ?O 

2.61 

64  oo 

12 

23.48 

/  oy 

9 

42 

04.00 
62.92 

i.  20 

0.90 

1-25 

trace  {*£ 

I  -3 

22  8p 

8.00 

2  44 

£               g 

2  V) 

O  QQ 

1  J 
14 

^c^.uy 

23.36 

8.07 

4.83 

58.93 

1.00 

0.50 

0.85* 

2.46 

English  Portland,  made  from  chalk  and  clay  found  at  Hull- 
English  Portland,  made  from  clay  and  alkali  waste. 
English  Portland,  given  by  Reid  as  first  quality. 
Belgian  Portland. 
Belgian  Portland. 
French  Portland. 
French  Portland. 
German  Portland. 
German  Portland. 
*  Calcium  sulfate.    f  Combined,     f  Moisture. 


COMPOSITION  OF  CEMENT  3 

11.  American   Portland  cement,  made  of  marl  and  blue  clay. 

12.  American  Portland,  made  from  clay  and  marl. 

13.  American  Portland,  made  from  argillaceous  limestone. 

14.  American  Portland,  made  from  argillaceous  limestone. 

Portland  cement,  according  to  Le  Chatelier,1  consists  of 
a  mixture  of  tricalcium  silicate/3CaO.SiOj  and  tricalcium 

aluminate,  3CaO.Al  O  .  He-arrived  at  this 
Composition  S  •  \ 

j.  P  conclusion  after  a  long  series  of  experiments, 

which  consisted  in  examining  thin  sec- 
tions of  cement  clinker  under  the  polarizing  microscope. 
He  also  made  experiments  upon  the  synthetic  production 
of  calcium  silicates  and  aluminates  by  heating  intimate 
mixtures  of  finely  pulverized  silica,  alumina,  and  lime. 
He  then  examined  into  the  hydraulic  properties  of  the 
compounds  so  prepared.  He,  however,  failed  to  prepare 
the  tricalcium  silicate  directly  by  heating  lime  and  silica, 
the  result  of  the  attempt  being  a  mixture  of  lower  silicates 
and  lime,  but  gave  it  as  his  opinion  that  this  compound 
could  be  prepared  indirectly  by  heating  together  a  mixture 
of  fusible  silicates  and  lime. 

The  tricalcium  silicate  is  the  essential  element  of  Port- 
land cement,  in  which  it  occurs  in  cubical  crystals.  In 
this  compound  the  lime  and  silica  bear  the  ratio  of  168:60.4 
or  2. 78:  i.  From  an  analysis  of  Tiel  " Grappiers  "  made 
by  Hauenschild,2  it  will  be  seen  that  they  are  approxi- 
mately pure  tricalcium  silicate. 

1  Annales  des  Mines,  1887,  p.  345. 

2  Thoniudustrie  Zeitung,  1883,  p.  418. 


4  INTRODUCTION 

ANALYSIS  OF  TIEI,  "  GRAPPIERS  " 

Per  cent. 

Silica         .  .  23.6 

Lime  .  .  .  -64.7 

Alumina    .  1.4 

Ferric  oxid       .  .  .0.8 

Magnesia  .  .  1.4 

Sulfuric  anhydrid  .  .  .0.5 

Water       ....  7-6 

100.0 

Ratio  of  lime  to  silica         .  .          2.74  :  i 

L,e  Chatelier  also  examined  thin  sections  of  hardened 
cement  under  the  microscope  and  found  that  it  consisted 
of  hexagonal  plates  of  crystallized  calcium 
'f  the  hydroxid,  Ca(OH)2,  embedded  in  a  white  ma- 
ar  enmg      ^.^  ^  interlaced  needle-shaped  crystals   of 
hydrated     monocalcium    silicate,    (CaSiO3)2. 
5H2O.     From  these  researches   he  concluded  that  the  tri- 
calcium  silicate  when  mixed  with  water  reacts  to  form  a 
hydrated  monocalcium  silicate  and  calcium  hydroxid  ac- 
cording to  the  reaction, 

(  2Ca3Si05)+  9H20  =  (CaSi03)2.5H20  +  4Ca(OH)2. 
The  calcium  hydroxid  then  probably  reacts  further  upon 
the  calcium  aluminate  of  the  cement,  forming  hydrated 
basic  calcium  aluminate,  Ca4Al2O7.i2H2O. 

Ca3Al206  +  Ca(OH)2  f  iiH2O  =  Ca4Al2O,.i2H2O 
The  "hardening"  of  cements  is  due  to  the  first  reaction, 
but  the  formation  of  the  hydrated  basic  calcium  aluminate 


H  YDRA  ULIC  INDEX  5 

probably  exerts  a  marked  influence  upon  the  '  '  setting  '  ' 
properties  of  the  cement. 

Assuming  that  three  molecules  of  lime  are  united  to  one 
of  silica  to  form  the  tricalcium  silicate,  that  three  mole- 

cules  of  lime  are  united  to  one  of  alumina  to 
»  ,  form  the  tricalcium  aluminate,  and  that  these 

two  compounds  are  the  essential  ingredients 
of  cement,  Le  Chatelier  gives  the  following  as  the  ratio 
between  the  lime  and  magnesia,  the  basic  elements,  and 
the  silica  and  alumina,  the  acid  elements  in  a  good  cement 

CaO  +  MgO    < 

Si02  +  A120S  =  3 
and 


Si02  —  A1203  —  Fe203  =    - 

Le  Chatelier  also  states  that  (i)  usually  gives  for  a  good 
cement  from  2.5  to  2.7,  and  (2)  from  3.5  to  4. 

This  ratio  between  the  silica  and  alumina  on  the  one 
hand  and  the  lime  on  the  other  is  termed  "hydraulic 
index.  '  ' 

Erdmenger1  has  pointed  out,  however,  that  the  .above 
equations  are  not  borne  out  by  experience,  as  the  assump- 
tion fiat  lime  and  magnesia  are  of  equal  hydraulic  value 
is  an  error. 

Messrs.  Spencer  B.  and  W.  B.  Newberry,1  in  a  series  of 
researches  as  to  the  constitution  of  cement,  arrived  at  con- 

1  j.  Soc.  Cheni.  Ind.,  n,  1035. 


6  INTRODUCTION 

elusions  quite  different  from  those  of  Le  Chatelier.  They 
prepared  silicates  and  aluminates  of  lime  synthetically  by 
Messrs  heating  together  in  a  Fletcher  gas  furnace 

Newberrys'  intimate  mixtures  of  finely  pulverized  quatrz 
Theories.  and  calcium  carbonate,  and  alumina  and  cal- 
cium carbonate  in  different  molecular  propor- 
tions. They  then  examined  into  the  hardening  and  set- 
ting properties  of  the  resulting  compounds.  While  these 
chemists  agreed  with  Le  Chatelier  that  the  silica  in  cement 
is  present  as  tricalcium  silicate,  and  that  to  this  is  due  the 
ultimate  hardening  of  cement,  they  found  no  difficulty  in 
preparing  the  tricalcium  silicate  directly,  by  heating  to- 
gether silica  and  lime  in  the  molecular  proportion  of  i  to  3. 
The  Messrs.  Newberry,  however,  from  their  experiments 
upon  the  calcium  aluminates  concluded  that  the  alumina 
is  in  combination  with  the  lime  as  dicalcium  aluminate 
and  not  as  tricalcium  aluminate.  Their  experiments  led 
them  to  the  following  conclusions  : 

"First. — Lime  may  be  combined  with  silica  in  the  pro- 
portion of  3  molecules  to  i ,  and  still  give  a  product  of 
practically  constant  volume  and  good  hardening  proper- 
ties, though  hardening  very  slowly.  With  3^  molecules  of 
lime  to  i  of  silica  the  product  is  not  sound,  and  crocks  in 
water. 

"Second. — Lime  may  be  combined  with  alumina  in  the 
proportion  of  2  molecules  to  i ,  giving  a  product  which  sets 
quickly,  but  shows  constant  volume  and  good  hardening 

1  J.  Soc.  Chem.  Ind.,  1897,  p.  889. 


SUBSTANCES  FOUND  IN  CEMENT  7 

properties.  With  2%  molecules  of  lime  to  i  of  alumina 
the  product  is  not  sound. ' ' 

The  formula  for  the  tricalcium  silicate,  3CaO.SiO2,  cor- 
responds to  2.8  parts  by  weight  of  lime  to  i  part  of  silica, 

and  the  formula  for  the  dicalcium  aluminate, 
Newberry  s  ,  ,  5. 

2CaO.Al  O  ,  corresponds  to  i.i  parts  of  lime 
Formula.  23' 

to   i   of  alumina.     From  this  the   following 

formula  is  given  as  representing  the  maximum  of  lime 
which  should  be  present  in  a  correctly  balanced  Portland 
cement;  per  cent  lime  —  per  cent  silica  X  2.8  +  per 
cent  alumina  X  i  •  i  • 

They  found  that  cement  prepared  synthetically  with 
lime,  alumina,  and  silica  proportioned  according  to  the 
above  formula  gave  good  results,  whereas  that  prepared 
by  L,e  Chatelier's  formula  was  unsound,  showing  the  lime 
to  be  in  excess. 

From  this  it  will  be  seen  that  the  essential  ingredients 
of  Portland  cement  are  lime,  silica,  and  alumina.  A  little 
of  the  alumina  is  always  replaced  by  ferric 
Substances  Qxid  and  SQme  of  the  Hme  by  magnesia. 
Found  in  Small  percentages  of  alkalies,  potash  and 
Cement.  .  ,  ,  .,.  .  . 

soda,  present  in  the  clay  as  silicates,  are  also 

in  cement,  while  the  most  thorough  burning  fails  to  drive 
off  all  the  carbon  dioxid  from  the  limestone  or  marl  in  the 
raw  mixture,  leaving  a  trace  in  the  finished  product.  This 
trace  is  increased  by  the  absorption  of  the  constituent  from 
the  atmosphere.  Coal  contains  sulfur  ;  this  when  burned 
becomes  sulfur  dioxid,  a  gas  which  is  absorbed  by  the  un- 


8  INTRODUCTION 

combined  lime  of  the  cement  mixture,  or  left  in  the  ash 
when  it  unites  with  lime  to  form  calcium  sulfate.  Some 
sulfur  also  enters  the  cement  from  the  clay  or  marl.  These 
are  the  chemical  constituents  for  which  cements  are  mainl}' 
analyzed.  Usually  it  is  sufficient  to  know  the  silica,  lime, 
alumina  and  ferric  oxid  together,  and  the  magnesia;  less 
often  the  alumina  and  ferric  oxid  separately,  the  sulfuric 
acid  and  the  carbon  dioxid;  while  more  rarely  yet  the  alka- 
lies, combined  water,  and  the  sulfur  present  as  sulfate  and 
sulfid  respectively. 

A  good  cement  contains  from  58  to  67  per  cent  lime, 
the  amount  depending  upon  the  relative  proportions  of 
silica  and  alumina,  and  also  upon  the  care 
with  which  the  cement  has  been  manufac- 
tured. Up  to  the  limit,  it  may  be  said,  that  the  more 
lime  that  is  present  in  a  cement  the  greater  will  be  its 
strength.  The  limit  is  reached,  however,  when  more  lime 
is  present  than  will  combine  chemically  with  the  silica 
and  alumina,  leaving  some  lime  in  the  uncombined  state, 
or,  as  Newberry  's  formula  puts  it,  when  the  percentage  of 
lime  is  greater  than  the  percentage  of  silica  multiplied  by 
2.8,  plus  the  percentage  of  alumina  multiplied  by  i.i. 
Lime  in  slaking  expands  so  that  an  excess  of  lime  over 
what  will  unite  with  the  silica  and  alumina  will  cause  the 
cement  to  expand,  or  "blow"  as  it  is  technically  termed, 
and  crack. 

If  the  lime  is  much  under  the  limit,  the  cement  will  con- 
tain clay  'in  excess,   for  the  lime  will   not  be  present  in 


AL  UMTNA  9 

sufficient  quantity  to  change  all  the  clay  to  silicates  and 
aluminates.  This  excess  of  clay,  of  course,  is  devoid  of 
cementing  qualities  and  may  be  looked  upon  as  just  so 
much  foreign  matter.  Though  it  will  not  cause  the  cement 
to  fall  to  pieces  subsequently,  it  takes  away  from  its 
strength  because  in  its  place  should  be  cement.  The 
amount  of  lime  a  cement  will  bear  depends  upon  the  care 
with  which  the  mixture  of  raw  materials  is  made.  Thus 
poorly  ground,  imperfectly  mixed  raw  materials  would 
probably  result  in  a  very  much  over-limed  cement,  if  the 
lime  limit  (as  shown  by  chemical  analysis  of  the  clay, 
marl,  limestone  or  cement  rock  of  the  mixture)  was  any- 
where near  reached;  for  the  coarse  particles  of  calcium  car- 
bonate would  not  come  into  sufficiently  close  contact  with 
the  silica  and  alumina  to  completely  combine  with  the  lat- 
ter. A  properly  burned  cement  will  also  stand  a  greater 
percentage  of  lime  than  an  improperly  burned  one.  A 
cement  in  which  the  temperature  at  burning  was  too  low 
to  heat  all  the  lime  to  the  point  of  combination  with  the 
silica  and  alumina,  would  naturally  contain  free  lime. 
Chemical  analysis,  therefore,  if  taken  alone  as  the  guide 
to  a  cement,  will  seldom  tell  us  much,  where  the  lime  con- 
tent is  concerned ;  as  of  two  cements  containing  the  same 
quantity  of  lime,  one  properly  made  might  be  quite  sound 
while  the  other,  from  faulty  mixing  and  burning,  might  be 
anything  but  sound.  A  method  of  determining  the  un- 
combined  lime  in  cement  would  enable  us  to  tell  whether 
a  given  cement  is  sound  or  not,  but  unfortunately  no 
method  of  accurately  determining  this  constituent  is  now 


I0  INTRODUCTION 

known,  so  that  the  physical  test  of  mixing  the  cement 
with  water  and  watching  it  for  cracks,  has  to  be  resorted 
to  as  a  test  for  free  lime  and  soundness. 

Portland  cement  usually  contains  between  5  and  10  per 
cent  alumina.  As  the  percentage  of  alumina  rises,  the 
cement  becomes  more  quick-setting.  When 
the  percentage  of  alumina  rises  above  10  per 
cent  the  cement  becomes  very  quick-setting,  with  a  cor- 
responding decrease  of  tensile  strength.  This  is  to  be  ex- 
pected, since  the  strength  of  cement  is  due  to  the  calcium 
silicate,  and  its  setting  properties  to  the  calcium  alumi- 
nate.  As  the  calcium  aluminate  is  very  fusible,  the 
clinkers  obtained  on  burning  mixtures  high  in  alumina 
are  very  fusible,  hard  to  burn  uniformly  and  difficult  to 
grind.  Cement  clinkers  made  from  kaolin  show  all  of 
these  properties  and  the  finished  cement  is  low  in  tensile 
strength. 

.  According  to  Le  Chatelier,  ferric  oxid  and  calcium  car- 
bonate on  burning  yield  products  which  slake  with  water 

and  possess  no  hydraulic  properties.    Schott, 
Feme  Oxid.    , 

however,    prepared    cement  containing   only 

lime,  silica  and  ferric  oxid,  which  showed  excellent  hard- 
ening qualities,  and  therefore  concluded  that  alumina  could 
be  completely  replaced  by  ferric  oxid  without  diminishing 
in  any  way  the  hydraulic  properties  of  cement.  S.  B.  and 
W.  B.  Newberry  from  their  researches  concluded  that  ferric 
oxid  and  alumina  act  in  a  similar  manner  in  promoting 
the  combination  of  silica  and  lime.  The  amount  of  ferric 


MAGNESIA  ii 

oxid  in  cements  is  usually  small,  less  than  5  per  cent,  and 
it  is  generally  agreed  that  when  not  in  excess  of  5  or  6  per 
cent  ferric  oxid  does  not  perceptibly  effect  the  construc- 
tive value  of  cement.  The  dark  gray  color  of  cement  is 
due  to  the  presence  of  iron  compounds.  Cement  prepared 
from  silica,  lime,  and  alumina  only  is  colorless,  but  upon 
replacing  the  alumina  by  ferric  oxid  the  cement  becomes 
gray. 

A  cement  containing  i  ^  per  cent  of   magnesia  was  long 
considered  dangerous;   now  3  per  cent  in  cement  is  thought 

to  be  harmless,  and  many  authorities  allow 
Magnesia.  ' 

even  5  per  cent  magnesia.  1  he  popular  sup- 
position is  that  magnesia  in  considerable  percentages 
causes  cement  in  time  to  expand  and  crack.  R.  Dj'ker- 
hoff  presented  to  the  German  Association  of  Cement  Manu- 
facturers in  1895  the  results  of  a  very  thorough  research 
into  the  effects  of  magnesia.  From  his  experiments  he 
concluded  that  magnesia,  whether  added  to  a  normal  mix- 
ture or  substituted  for  an  equivalent  portion  of  lime,  causes 
a  decrease  of  strength  in  the  resulting  cement,  when  pres- 
ent in  more  than  4  per  cent.  Cracking  only  occurred  with 
8  per  cent  or  more  magnesia,  A  commission  from  the 
above  association  is  now  studying  the  effects  of  magnesia. 
Le  Chatelier  in  his  formula  considers  magnesia  to  replace 
lime,  while  the  Newberrys  in  their  formula  consider  it  in- 
active and  not  to  replace  lime.  The  latter  is  probably  the 
correct  supposition. 

Potash   and  soda  are  present  in  all  cements  in  small 


12  INTRODUCTION 

quantities  varying  from  0.5  to  2.5  per  cent.   Cements  made 
from  the  lime  waste  of  alkali  works  often  contain  over  this 

amount.  Butler1  states  that  instances  have 
Alkalies.  ...  1-1-1. 

occurred  in  which  these  cements  gave  any- 
thing but  satisfactory  results,  and  the  only  fault  that 
could  be  found  with  their  chemical  composition  was  a 
slight  excess  of  alkali.  Inmost  cement  the  alkalies  are 
present  in  such  small  quantity  that  their  effects  are  of 
little  importance.  The  old  theory  was  that  the  presence 
of  the  alkalies  promoted  the  combination  of  the  lime  with 
the  silica  and  alumina.  This  does  not  seem  to  be  borne 
out  by  experiments,  however,  and  the  presence  of  the 
alkalies  is  not  now  looked  upon  as  essential  to  the  forma- 
tion of  cement. 

Several  compounds  of  sulfur  are  present  in  cement;  chief 
of  these  are  calcium  sulfate  and  calcium  sulfid.  The  action 
„  lf  of  calcium  sulfate  upon  cement  is  to  delay 

the  set.  For  this  reason  it  is  often  added  in 
the  form  of  gypsum  to  the  cement  after  burning.  The 
Association  of  German  Cement  Manufacturers  so  far  recog- 
nize the  beneficial  effect  of  the  addition  as  to  allow  manu- 
facturers to  employ  a  proportion  not  exceeding  2  per  cent 
in  order  to  confer  to  the  cement,  slow-setting  properties. 
Although  the  presence  of  calcium  sulfate  in  small  quanti- 
ties is  beneficial  to  cement,  there  is  no  doubt  that  a  quan- 
tity exceeding  4  or  5  per  cent  is  injurious.  The  French 

1  "Portland Cement,"  by  D.  B.  Butler,  p.  263. 

2  German  Standard  Rules. 


CARBON  DIOXID  13 

specifications1  exclude  all  cements  which  contain  over  i 
per  cent  sulfuric  acid,  but  most  engineers  in  this  country 
in  their  specifications,  if  they  mention  it  at  all,  allow  2  per 
cent  of  sulfur  trioxid,2  SO  . 

Calcium  sulfid  is  objectionable  in  cement  from  the  fact 
that  it  reacts  with  the  iron  compounds  of  the  cement,  form- 
ing iron  sulfid.  This  latter  absorbs  oxygen  from  the  air, 
forming  iron  sulfate,  and  this  reaction  causes  expansion 
and  disintegration. 

Carbon  dioxid  is  present  in  all  cements.     If  present  in 

appreciable  quantity  it  shows  either  a  poorly  burned  ce- 

ment ;   that  is,  one  in  which  the  heating  was 

n-     . ,  not  carried  to  the  point  of  driving  out  all  the 

carbon  dioxid  from  the  calcium  carbonate,  or 

else  a  cement  containing  free  lime,  which  has  absorbed 

this  constituent  from   the  air.     As  natural  cements  are 

lighter  burned  than  Portlands  they  contain  a  much  larger 

percentage  of  carbon  dioxid,  as  the  table  given  below  will 

show. 

1  French  Government  specifications. 

2  Specifications  for  municipal  work  in  St.  I,ouis,  Mo. 


INTRODUCTION 


ANALYSIS  OF  NATURAL  CEMENTS 

Made  by  Julian  O.  Hargrove,  Asst.  Inspector  of  Asphalts  and  Cements, 
Washington,  D.  C. 


Brand. 

SiO2. 
Per 
cent. 

^ 
cent. 

Fe»03. 
Per 
cent. 

CaO. 
Per 
cent. 

MgO. 
Per 

cent. 

C02. 
Per 
cent. 

Cumberland 

29.92 
28.30 
29.00 
28.44 
28.36 

11.23 
IO.OO 

10.40 

9.68 

10.42 

4.78 
4-56 
2.90 
4.28 

4-15 

36.50 
49.60 

32.41 
36.06 
45-H 

11.63 
376 
19.92 
16.04 

3-82 

5-42 
3.01 
5.29 

4-75 
4.02 

Cumberland  &  Potomac 

P  T 

NOTE. — A  very  complete  presentation  of  the  more  tenable 
views  regarding  the  composition  and  hardening  of  cements  will 
be  found  in  an  article  "  Ueber  die  Untersuchung  und  das  Verhal- 
ten  von  Cement"  by  Dr.  R.  Zsigmondy  in  Dingler's  polytech- 
niches  Journal,  294,  89,  114,  137,  163. 


ANALYTICAL  METHODS 


THE  ANALYSIS  OF  CEMENT 
Preparation  of  the  Sample 

The  knowledge  usually  sought  by  a  chemical  analysis  of 
cement  is  the  average  composition  of  a  given  lot  or  bin . 
In  order  that  it  shall  give  this,  it  is  necessary 
that  the  small  sample  used  in  the  analysis 
shall  fairly  represent  the  whole  quantity,  possibly  many 
tons.  In  a  large  lot  of  cement,  it  is  hardly  probable  that 
a  small  sample,  or  even  a  large  sample,  taken  from  one 
place  in  the  bin  or  one  barrel  in  the  consignment,  will  have 
the  average  composition  of  the  cement,  since  this  particu- 
lar point  in  the  bin,  or  this  special  barrel,  might  be  better 
or  worse  than  the  remainder.  It  is  well  in  sampling  from 
a  bin  to  take  small  samples  from  various  points,  not  merely 
upon  the  surface  where  the  cement  may  have  become 
slightly  damaged  by  exposure  to  air  or  damp,  but  also  un- 
derneath by  using  a  fairly  long  brass  tube.  This  latter 
should  be  slipped  over  a  stick  turned  to  fit  the  tube  and 
having  a  sharp  end.  When  thrust  deep  enough  into  the 
pile,  the  stick  should  be  withdrawn  from  the  tube  and  this 
then  pushed  a  little  farther  into  the  pile.  The  cement  in 
the  end  of  the  tube  when  withdrawn  will  furnish  the  sam- 
ple. In  sampling  shipments  it  is  best  to  take  a  sample 
from  ten  or  more  bags  or  barrels  in  each  one  hundred  tons 


1 6  ANALYTICAL  METHODS 

going  for  it  well  down  into  the  heart  of  the  bag  or  barrel, 
and  not  at  the  mouth.  The  samples  may  then  be  placed 
in  a  clean  paper  bag,  labeled  and  taken  to  the  laboratory, 
where  they  should  be  well  mixed,  and  the  bulk  reduced  to 
laboratory  dimensions  by  halving  down.  To  do  this,  pour 
the  sample  upon  a  piece  of  clean  paper,  mix  well  and  di- 
vide the  pile  into  quarters  with  a  spatula.  Brush  away 
two  of  the  diagonally  opposite  quarters  with  a  small  i  y2  - 
inch  flat  brush.  Mix  thoroughly  the  remaining  two  quar- 
ters and  divide  as  before.  Repeat  this  until  the  sample  is 
reduced  sufficiently.  The  final  sample  is  now  ground  to 
the  proper  fineness,  and  if  to  be  preserved,  placed  in  a 
stoppered  bottle  and  kept  in  a  dark  place.  If  for  immedi- 
ate use,  a  sample  or  coin  envelope  may  be  substituted  for 
the  bottle. 

Often  the  chemist  receives  his  sample  from  that  sent  the 
engineer  in  charge  of  the  physical  testing  laboratory.  In 
this  case  the  mixing  should  have  been  already  done  and 
the  bulk  is  small,  so  that  only  the  grinding  has  to  be 
done. 

In  order  that  the  solvents  and  fluxes  used  in  decompo- 
sing the  cement  for  analysis  may  do  their  work  thoroughly, 

Grinding  Jt  is  necessary  that  the  final  sample  be  in  the 
condition  of  a  fine  powder,  free  from  any  grit 
or  hard  particles.  Cement  is  already  ground  more  or  less 
to  such  an  impalpable  state.  Cement  of  the  better  grades 
is  now  pulverized  so  finely  that  only  from  5  to  TO  per  cent 
is  rejected  by  a  sieve  of  2,500  meshes  per  square  inch. 


DRYING  17 

Still  the  sample  should  be  freed  from  all  grit  before  weigh- 
ing the  portions  to  be  used  for  the  various  determinations. 
Unless  a  very  complete  analysis  has  to  be  made,  from  5  to 
6  grams  of  cement  are  placed  in  an  agate  mortar,  a  little 
at  a  time,  according  to  the  size  of  the  mortar  and  ground 
until  no  grit  remains,  as  ascertained  by  rubbing  between 
the  fingers,  or  on  the  back  of  the  hand,  or  biting  with  the 
teeth.  When  alkalies,  combined  water,  etc.,  are  to  be  de- 
termined or  check  analyses  are  to  be  run,  it  will  probably 
be  necessary  to  grind  a  larger  quantity  than  6  grams. 
From  the  size  and  shape  of  the  ordinary  agate  mortar  and 
pestle  the  operation  of  grinding  is  very  fatiguing.  It  may 
be  much  facilitated,  however,  by  cutting  a  hole,  of  such 
size  and  shape  as  to  hold  the  mortar  firmly,  in  the  middle 
of  a  block  of  hardwood,  a  foot  or  so  square.  The  pestle 
is  then  fixed  in  a  piece  of  round  brass  tubing  of  sufficient 
bore,  or  else  in  a  round  hard  wood  handle.  Several  me- 
chanical grinders  are  on  the  market,  descriptions  of  which 
may  be  found  in  the  trade  catalogues  of  most  of  the  prom- 
inent dealers  in  chemical  apparatus. 

The  finely  ground  sample  will  now  contain  more  or  less 
hygroscopic  moisture.     This  should  be  gotten  rid  of  bv 
.  spreading  the  sample  upon  a  watch-glass  in 

an  oven  and  drying  for  one  hour  at  a  temper- 
ature of  from  ioo°-no°  C.  It  is  then  removed,  poured 
into  a  clean  dry  test-tube  while  still  hot,  and  tightly  corked; 
or  the  cement  may  be  placed  in  the  test-tube  instead  of  the 
watch-glass  and  thus  dried. 


j8  ANALYTICAL  METHODS 

Instead  of  drying  the  sample  some  analysts  prefer  to  de- 
termine the  moisture  and  report  the  amount  found  in  their 
analysis.  To  do  the  latter,  place  i  gram  of  the  sample  in 
a  previously  weighed  platinum  or  porcelain  crucible,  a 
watch-glass,  or  a  weighing  tube.  Take  the  weight  of  the 
whole  and  dry  in  an  oven  at  105°-:  10°  C.  for  one  hour,  or 
until  no  further  loss  in  weight  occurs.  Weigh  again;  the 
loss  represents  moisture. 

Any  of  the  three  forms  of  oven  described  below  will  be 
found  useful  for  drying  cement  samples,  precipitates,  etc. 
The  first  two  can  be  purchased  from  dealers  and  the  third 
can  easily  be  made  from  "scraps  "  around  the  laboratory. 

The  ordinary  steam  oven  is  made  of  copper,  doubly  cased 
throughout  with  the  exception  of  the  door.  The  casing 
is  filled  at  its  opening  to  about  three-fourths  of  its  height 
with  water  and  heat  applied  b}'  a  Bunsen  burner  under- 
neath. When  the  water  boils,  the  upper  part  of  the  casing 
becomes  full  of  steam  and  the  temperature  of  the  oven  ap- 
proaches 100°  C.  Unless  provided  with  an  arrangement 
for  maintaining  a  "constant  water-level,"  they  require 
watching  in  order  to  prevent  the  boiling  off  of  the  water. 

When  a  temperature  above  100°  C.  is  required,  the  air- 
bath  must  supplant  the  steam  oven.  The  construction  is 
similar  to  that  of  the  latter,  except  that  the  casing  is  sin- 
gle. Air-baths  are  usually  provided  with  false  bottoms  of 
sheet  iron  in  order  to  prevent  the  destruction  of  the  real 
one  of  copper  by  the  burner  flame.  It  is  necessary  to  con- 
trol the  temperature  of  the  air-bath,  however,  by  a  ther- 


DRYING 


mometer  inserted  through  a  cork,  in  the  opening,  in  the 
top  of  the  oven .  The  required  temperature  can  be  main- 
tained by  adjusting  the  stop-cock  of  the  gas  supply.  After 
the  gas  has  once  been  regulated  the  temperature  will  re- 
main constant  for  some  hours.  Gas  regulators,  called 
"thermostats,"  can  be  purchased  from  dealers  in  chem- 
ists' supplies,  and  while  they  are  liable 
to  become  clogged  and  get  out  of  order, 
they  still  are  very  convenient  for  keep- 
ing a  constant  temperature. 

The  author  recently  described  (in  the 
Scientific  American,  vol.  Ixxx,  p.  230)  a 
form  of  drying  oven  which  he  has  used 
successful!}-  in  his  laboratory  for  some 
years.  •  It  is  non-corrosive,  simple  and 
cheap.  In  themetal  ovens,  the  acid  fumes, 
given  off  in  "baking"  certain  substances, 
attack  the  metal,  forming  a  scale  which, 
in  spite  of  care,  will  sooner  or  later  drop 
in  some  sample  or  dish  drying  in  the 
oven.  Fig.  i  shows  the  oven.  Select  a 
large  glass  bottle  and  cut  off  the  bottom 
by  making  a  mark  on  it  with  a  file,  wrap- 
ping two  strips  of  wet  paper,  one  a  little 
above  and  one  a  little  below  the  mark, 
and  revolving  the  bottle  slowly  and  evenHT 
while  the  tip -of  a  small  blowpipe  flame 
or  small  flame  from  a  blast-lamp  plays  on  the  space  be- 


20  ANALYTICAL  METHODS 

tween  the  paper.  ,  A  crack  will  start  in  a  few  moments, 
which  will  follow  the  flame  around  the  bottle.  The  sharp 
edges  should  be  smoothed  by  a  file  dipped  in  turpentine, 
and  a  narrow  strip  of  asbestos  wound  around  the  neck  for 
a  handle.  The  upper  half  of  the  bottle  is  placed  upon  a 
sand-bath  or  hot  plate,  and  the  object  to  be  heated,  upon  a 
support  of  glass  or  porcelain,  raised  above  the  sand-bath 
by  a  wire  bent  to  form  a  tripod.  The  temperature  is  regu- 
lated by  a  thermometer  thrust  through  a  cork  in  the  mouth 
of  the  bottle.  Large  grooves  should  be  cut  lengthwise 
along  the  cork  to  make  a  free  escape  for  the  steam  and 
vapors,  and  to  create  a  current  of  hot  air  through  the 
oven.  Both  this  and  the  other  form  of  air-bath  described 
should  be  set  in  a  corner  shielded  from  air  drafts.  If 
this  is  done  the  maintaining  of  a  constant  temperature 
will  be  much  simplified. 

Determination  of  Silica,  Ferric  Oxid  and  Alumina, 
Lime  and  Magnesia 

The  chemical  elements  which  go  to  make  up  limestones, 
cements,  and  clays  are  the  same,  varying  only  in  propor- 
tions and  state  of  combination,  yet  these  dif- 
Notes  on  the  r 

Decomposi  *erences  are  such  that  while  limestones  are 
tion  of  Ce-  decomposed  by  quite  dilute  hydrochloric  acid, 
ment  clays  are  practically  unacted  upon  by  that 

acid  even  when  concentrated.  Analytically 
cements  lie  on  the  one  side  between  limestones  and  marls, 
which  are  easily  decomposed  by  dilute  hydrochloric  acid, 


DECOMPOSITION  OF  CEMENT  21 

and  on  the  other,  clays  and  refractory  silicates  requiring 
for  decomposition  fusion  with  alkaline  carbonates. 

'  If  a  limestone  is  treated  with  hydrochloric  acid  of  1.07 
sp.  gr.  the  decomposition  will  be  practically  complete  and 
the  small  amount  of  silica  usually  found  in  limestones, 
when  separated  by  evaporation,  will  be  found  nearly  free 
from  impurities.  If,  however,  the  percentage  of  silica  is 
high,  the  impurities  rise  greatly  ;  especially  is  this  the 
case  when  the  limestone  also  contains  much  alumina. 
With  Portland  cement  acid  of  this  strength  fails  to  bring 
about  complete  decomposition  and  the  silica  resulting  from 
the  treatment  will  be  much  less  pure  than  that  from  a 
limestone.  If,  however,  the  strength  of  the  acid  is  in- 
creased to  about  i.io  sp.  gr.,  the  decomposition  of  the  ce- 
ment is  nearly  complete  and  in  a  freshly  burned  Portland 
cement  the  percentage  of  the  other  constituents  left  with 
the  silica  is  so  small  as  to  be  hardly  worth  accounting  for 
in  a  technical  analysis.  Fusion  of  either  the  sample  di- 
rectly, or  the  impure  silica  obtained  by  treatment  with 
acid  of  the  strength  last  indicated,  with  sodium  carbonate 
or  a  mixture  of  sodium  and  potassium  carbonates  undoubt- 
edly gives  much  more  accurate  results.  Still  where  rapid 
analyses  are  required,  especially  at  the  cement  mill  itself, 
where  the  analysis  of  freshly  burned  cement  is  usuall}' 
that  desired,  the  decomposition  by  means  of  dilute  hydro- 
chloric acid  (i  to  i)  is  usually  employed,  and  it  gives  re- 
sults which  are  sufficiently  near  the  truth  for  checking  the 
quality  of  the  product.  In  analyzing  unknown  brands  of 


22  ANALYTICAL  METHODS 

cement,  or  cement  which  has  stood  for  sometime,  or  where 
great  accuracy  is  desired,  it  is  best  to  use  one  of  the 
methods  depending  upon  the  decomposition  by  ignition 
or  fusion  with  alkaline  carbonates,  thus  insuring  a  com- 
plete breaking  up  of  the  silicates. 

When  calcium  and  magnesium  are  precipitated,  as  oxa- 
late  and  phosphate  respectively,  from  solutions  containing 
much  sodium  or  potassium  salts,  the  precipitates  are  almost 
sure  to  be  contaminated  with  alkaline  .salts.  Even  much 
washing  fails  to  remove  the  impurity  from  the  precipitate. 
When,  therefore,  the  sample  of  cement  has  been  fused  di- 
rectly with  from  5  to  10  grams  of  sodium  carbonate,  there 
is  sure  to  be  this  danger  that  the  lime  and  magnesia  pre- 
cipitates will  carry  down  some  sodium  salts,  from  which 
subsequent  washing  will  fail  to  free  them.  In  accurate 
work  this  error  can  be  eliminated  by  reprecipitation.  If 
instead  of  fusing  the  sample  directly  with  five  to  eight 
times  its  weight  of  sodium  carbonate,  the  impure  silica, 
separated  by  treatment  with  hydrochloric  acid,  is  fused 
with  an  equal  bulk  of  sodium  carbonate,  the  quantity  of 
sodium  salts  introduced  into  the  solution  will  be  reduced 
to  one-fourth,  usually  between  i.o  and  1.5  gram  of  sodium 
chlorid. 

To  save  reprecipitation  of  the  lime  and  magnesia,  and 
at  the  same  time  break  up  the  silicates,  Dr.  Porter  W. 
Shimer,  of  Lafayette  College,  has  devised  a  method  de- 
pending upon  a  fact  which  he  discovered,  that  ignition 
with  sodium  carbonate  even  in  the  proportion  of  i  gram  of 


SILICA  23 

cement  to  0.5  gram  of  sodium  carbonate  serves  com- 
pletely to  break  vip  the  silicates.  The  quantity  of  sodium 
salts  introduced  into  the  solution  from  0.5  gram  of  carbon- 
ate is  so  small  that  possible  contamination  of  the  lime  and 
magnesia  precipitates  is  done  away  with.  On  heating 
cement  and  sodium  carbonate  together  in  this  proportion 
no  fusion  takes  place,  only  a  sintering.  This  method  is 
given  first  of  the  four  as  the  author  believes  it  to  be  best 
for  general  use.  Where  technical  requirements  demand 
rapidity  the  method  of  solution  in  hydrochloric  acid  with- 
out fusion  will  be  found  satisfactory. 

By  Ignition  of  the  Sample  with  Sodium  Carbonate 
Weigh  i  gram  of  the  finely  ground  dried  cement  into  a 
platinum  crucible  and  mix  intimately  by  stirring  with  a 
glass  rod  with  0.5  gram  of  pure  dry  sodium 
carbonate.  Brush  off  the  rod  into  the  cruci- 
ble with  a  camel's  hair  brush.  Cover  the  crucible  and 
place  over  a  low  flame.  Gradually  raise  the  flame  until 
the  crucible  is  red  hot  and  continue  the  heating  for  five 
minutes  longer  ;  the  nplace  over  a  blast-lamp  and  heat  five 
minutes  more.  While  still  hot,  plunge  the  bottom  of  the 
crucible  half  the  way  up  into  cold  water.  This  will 
loosen  the  mass.  Drop  the  mass  into  a  casserole  or  dish 
and  cover  the  latter  with  a  watch-glass.  Pour  into  the 
crucible  a  portion  of  a  mixture  of  30  cc.  of  hot  water  and 
10  cc.  of  dilute  hydrochloric  acid.  Heat  on  a  hot  plate, 
and  then  pour  into  the  dish  or  casserole.  Clean  out  the 
crucible  with  a  rubber-tipped  rod,  using  the  rest  of  the 


24  ANALYTICAL  METHODS 

mixture  of  acid  and  water.  To  the  solution  in  the  casse- 
role add  a  few  drops  of  concentrated  nitric  acid  and  evapo- 
rate to  dryness  on  a  hot  plate  or  water-bath,  using  care  to 
prevent  spattering.  Heat  the  dry  mass  until  all  odor  of 
hydrochloric  acid  has  disappeared.  This  can  be  done 
safest  in  the  oven  described  on  page  19  at  110°  C. 
Add  15  cc.  of  dilute  hydrochloric  acid  to  the  contents  of 
the  dish  and  digest  a  few  moments,  then  dilute  to  50  cc. 
with  hot  water,  filter  and  wash  well  with  hot  water.  Dry 
the  precipitated  silica  by  placing  paper  and  residue  in  a 
previously  weighed  crucible,  and  setting  over  a  low  flame. 
Ignite  and  weigh  as  silica,  SiO2.  Calculate  the  percentage 
and  report  as  such. 

Heat  the  filtrate  from  the  silica  to  boiling,  add  ammonia 
in  slight  but  distinct  excess,  boil  five  minutes,   allow  to 

settle,  filter  in  a  beaker  capable  of  holding  i 
Ferric  Ox  id 
andAlumina       er'    a        wasn   tne  precipitate  a  few  times 

with  hot  water.  Redissolve  the  precipitate  in 
hydrochloric  acid  by  pouring  the  acid  around  the  edges  of 
the  paper  and  stirring  up  the  precipitate  with  a  jet  of 
water  from  a  wash-bottle.  Allow  the  solution  to  run  into 
the  beaker  in  which  the  precipitation  was  made.  Wash 
the  paper  well  with  cold  water.  Bring  the  hydrochloric 
acid  solution  to  boiling,  add  ammonia  in  slight  but  dis- 
tinct excess  and  filter.  Allow  the  filtrate  to  run  into  that 
from  the  first  precipitation.  Wash  the  precipitate  well 
with  hot  water,  dry,  ignite,  and  weigh  as  ferric  oxid  and 
alumina.  To  determine  separately  the  Fe2O?  and  the  AlaO?) 


MAGNESIA  25 

refer  to  ' '  Determination  of  Ferric  Oxid  ' '  and  subtract  the 
percentage  of  ferric  oxid  found  from  the  combined  percent- 
age of  ferric  oxid  and  alumina  ;  the  difference  will  be  the 
alumina,  A12O3. 

Dilute  the  combined  nitrates  to  about  800  cc.,  if  not 
already  so,  bring  to  a  boil,  make  strongly  ammoniacal, 
and  add  25  cc.  of  a  saturated  solution  of  am- 
monium oxalate.  Stir  a  little  and  let  stand 
one  hour.  Filter,  wash  well  with  hot  water,  dry  and  ig- 
nite, first  over  a  Bunsen  burner  until  all  the  carbon  is  burned 
off,  and  then  over  a  blast-lamp  for  fifteen  minutes.  Cool 
and  weigh.  Again  heat  for  five  minutes  over  a  blast-lamp 
and  weigh.  Repeat,  if  necessary,  until  the  weight  is  con- 
stant, that  is,  two  weights  agree  to  within  0.0002  gram  of 
each  other.  The  ignition  has  changed  the  precipitate  to 
calcium  oxid,  CaO.  Weigh  as  such  and  calculate  the  per- 
centage. 

Concentrate  the  filtrate  somewhat  by  evaporation  after 
acidifying  slightly  with  hydrochloric  acid,  and  adding  20 
cc.  of  sodium  phosphate.  Set  the  solution  in 
a  vessel  of  water  to  cool,  and  then  add,  drop 
by  drop,  from  a  burette,  with  constant  stirring,  ammonia 
until  slightly  ammoniacal  and  the  precipitate  begins  to 
appear.  Stop  adding  ammonia,  stir  for  five  minutes,  add 
one-tenth  the  volume  of  the  liquid  of  strong  ammonia  and 
stir  for  three  minutes.  Allow  the  solution  to  set  in  a  cool 
place  over  night,  filter  in  the  morning,  and  wash  well  with 
a  mixture  of  i  liter  water,  500  cc.  ammonia  (0.96  sp.  gr.), 


26  ANALYTICAL  METHODS 

and  150  grams  ammonium  nitrate.  Dry,  ignite,  and  weigh 
as  magnesium  pyrophosphate,  Mg2P2O7,  which  multiplied 
by  0.36190  gives  the  equivalent  of  magnesia,  MgO. 

By  Solution  of  the  Sample  in  HC1  and  Fusion  of  the  Insoluble 
Residue  with  Na2COs 

Weigh  i  gram  of  finely  ground  dried  cement  into  a  5  inch 
casserole,  add  30  cc.  of  hydrochloric  acid  (sp.  gr .  i .  10)  and  2 
cc.  of  nitric  acid.  Evaporate  to  dryness  and  heat 
at  110°  C.  until  all  smell  of  hydrochloric  acid 
is  gone.  Add  15  cc.  dilute  hydrochloric  acid  and  100  cc. 
water,  heat  to  boiling  and  filter.  Ignite  the  residue  upon 
the  filter  in  a  platinum  crucible  until  all  the  carbonaceous 
matter  of  the  paper  is  burned,  fuse  with  1.5  gram  of  so- 
dium carbonate,  first  over  a  Bunsen  burner,  and  then  over 
a  blast-lamp,  until  the  contents  of  the  crucible  are  in  quiet 
fusion.  Remove  the  crucible  from  the  flame  and  run  the 
fused  mass  well  up  on  the  sides  of  the  crucible  by  tilting 
and  revolving  the  latter  while  held  with  the  crucible  tongs. 
While  still  hot  plunge  the  crucible  three-quarters  of  the 
way  into  clean  cold  water,  which  will  frequently  cause 
the  mass  to  loosen  from  the  sides  of  the  crucible.  Wash 
off  any  of  the  material  spattered  on  the  crucible  cover 
into  a  casserole  with  hot  water,  and  add  the  fused  mass 
in  the  crucible  if  it  has  come  loose.  If  not,  fill  the  cruci- 
ble with  hot  water  and  digest  on  the  hot  plate  until  the 
fused  mass  softens  and  can  be  removed  to  the  casserole. 
Clean  the  crucible  with  water,  dissolving  in  dilute  hydro- 
chloric acid  any  particles  adhering  too  firmly  to  the  cruci- 


FERRIC  OXID,  ALUMINA,  LIME,  MAGNESIA    27 

ble  to  be  removed  from  it  by  gentle  rubbing-  with  a  rubber- 
tipped  rod.  When  the  hot  water  has  thoroughly  disinte- 
grated the  fusion,  cover  the  casserole  with  a  watch-glass 
and  strongly  acidify  the  contents  with  hydrochloric  acid. 
Heat  until  effervescence  ceases  and  everything  dissolves 
except  silica.  Wash  off  the  watch-glass  and  evaporate 
the  solution  to  dryness.  Heat  for  one  hour  at  110°  C.,  or 
until  all  odor  of  hydrochloric  acid  has  disappeared,  add 
100  cc.  hydrochloric  acid  and  50  cc.  water,  warm  until  all 
soluble  salts  are  in  solution,  filter,  wash  well  with  hot 
water,  dry,  ignite,  and  weigh  as  silica,  SiO,. 

Mix  the  two  nitrates  from  the  silica  separations  and  pro- 
ceed to  determine  iron  and  alumina,  lime  and  magnesia, 
as  directed  in  the  foregoing  method.     A  much 

'  better  way,  however,  would  be  not  to  mix  the 
Alumina,  .    . 

Lime  and  two  fi^trates'  but  to  precipitate  the  iron,  alu- 
Magnesia  mina,  lime,  and  magnesia  in  each  filtrate  sep- 
arately, as  the  precipitate  of  calcium  oxalate 
is  almost  sure  to  carry  down  some  sodium  salts.  If  de- 
sired, the  precipitates  of  a  kind  may  be  ignited  together  in 
the  same  crucible.  The  author  adopts,  when  using  this 
method,  the  plan  of  holding  back  the  main  filtrate  (that 
from  the  impure  silica)  and  dissolving  the  precipitate  from 
the  second  filtrate  (that  from  the  pure  silica)  in  a  little 
dilute  hydrochloric  acid  after  washing  once  or  twice  with 
water,  and  adding  it  to  the  main  filtrate  just  before  ma- 
king the  corresponding  precipitation  in  the  main  filtrate. 
For  example,  the  slight  precipitate  of  iron  and  alujnina 


28  ANALYTICAL  METHODS 

obtained  on  adding  ammonia  to  the  second  filtrate  from 
the  silica,  would  be  dissolved  in  hydrochloric  acid  and  the 
solution  added  to  the  main  nitrate  before  adding  ammonia 
to  the  latter  to  precipitate  the  main  body  of  the  ferric  oxid 
and  alumina. 

Some  chemists  merely  determine  the  iron  and  alumina 
in  the  filtrate  from  the  silica  by  fusion,  disregarding  any 
calcium  and  magnesium  which  might  have  been  carried 
down  with  the  impure  silica,  as  inappreciable.  Dr.  Shinier 
has  shown1  that  this  quantity  is  not  so  small,  and  hence  it 
is  advisable  to  determine  also  the  lime  and  magnesia  in 
the  second  filtrate. 

By  Fusion  of  the  Sample  Itself  with  Sodium  Carbonate- 
Weigh  i  gram  of  the  finely  ground  cement  and  mix  with 
about  6  grams  of  dry  sodium  carbonate  ;  transfer  to  a  plati- 
num crucible  and  fuse,  first  at  a  low  heat,  then 
Silica. 

for  about  twenty  minutes  in  the  flame  of  the  blast 

lamp.  After  fusion  cool  the  crucible  and  place  in  a  beaker 
with  50  cc.  of  hot  water  and  20  cc.  of  strong  hydrochloric 
acid.  Cover  the  beaker  with  a  watch-glass,  placeon  a  steam- 
bath,  and  allow  to  remain  until  the  fused  mass  has  com- 
pletely dissolved.  Remove  the  watch-glass  and  crucible, 
rinsing  both  with  hot  water,  add  a  few  drops  of  nitric  acid, 
and  evaporate  the  contents  of  the  crucible  to  dry  ness; 

1  J.  Am.  Chem.  Soc.,  21,  289. 

2  Method  as  used  by  Julian   O.  Hargrove,   Assistant  Inspector  of  As- 
phalts and  Cements  of  the  District  of  Columbia. 


LIME  29 

moisten  the  residue  with  a  few  drops  of  hydrochloric  acid 
and  again  evaporate  to  dn^ness.  Place  the  beaker  in  an 
air-bath  and  heat  at  a  temperature  of  110°  C.  until  all  odor 
of  acid  has  disappeared.  Add  15  cc.  dilute  hydrochloric 
acid  and  30  cc.  hot  water ;  after  standing  a  few  minutes 
filter  through  a  weighed  Gooch  crucible  into  a  200  cc. 
graduated  flask,  wash  with  hot  water,  dry,  ignite,  and 
weigh  as  silica,  SiO2. 

Dilute  the  filtrate  in  the  graduated  flask  to  the  200  cc. 
mark.     Remove  100  cc.  (with  a  pipette)  to  a  beaker,  bring 

.     to  a  boil,  add  ammonia  in  slight  but  distinct 
Ferric  Oxid 

and  Alu-  excess,  boil  a  few  minutes,  allow  to  stand 
mina  until  the  precipitate  has  settled,  and  filter 

through  a  weighed  Gooch  crucible,  taking 
care  not  to  disturb  the  precipitate.  Dissolve  the  precipi- 
tate in  a  few  cubic  centimeters  of  hot  dilute  hydrochloric 
acid,  add  25  cc.  of  hot  water,  and  reprecipitate  with  ammo- 
nia. Filter,  wash  with  hot  water,  dry,  ignite,  and  weigh. 
The  increased  weight  multiplied  by  2  gives  the  weight 
of  ferric  oxid  and  alumina. 

Mr.  Hargrove  determines  the  iron  in  the   remaining  100 
.  cc.  of  the  filtrate  from  the  silica,  by  reduction 

with  stan nous  chlorid  and  titration  with  bi- 
chromate solution.     See  "  Determination  of  Ferric  Oxid. " 
To  the  filtrate  from  the  iron  and  alumina  add  ammonia 
until  slightly  alkaline,   heat  to  boiling  and 
add  drop  by  drop  a  saturated  solution  of  am- 
monium oxalate  until  in  slight  excess,  continue  the  boil- 


3o  ANALYTICAL  METHODS 

ing  for  a  few  minutes  and  then  allow  to  stand  about  one 
hour  for  the  precipitate  to  settle.  Filter  through  a  small 
filter,  wash  the  precipitate  with  water  to  which  a  little  am- 
monia has  been  added,  dry,  transfer  to  a  weighed  platinum 
crucible,  and  ignite,  first  at  a  low  heat,  then  in  the  flame 
of  a  blast-lamp  for  about  twenty  minutes.  Allow  the  cru- 
cible to  cool,  moisten  the  contents  with  a  few  drops  of  con- 
centrated sulfuric  acid,  cover  and  place  the  crucible  in  an 
inclined  position  on  a  triangle  over  a  low  flame.  Apply 
heat  gently  at  the  top  of  the  crucible,  continuing  the  heat- 
ing until  fumes  of  sulfuric  acid  cease,  then  raise  the  flame 
until  the  crucible  is  a  faint  red.  Cool  and  weigh.  Multi- 
ply this  weight  by  2  and  then  by  0.41185  for  the  lime, 
CaO,  in  the  cement. 

Evaporate  the  filtrate  to  about  150  cc.,  cool,  add  5  cc.  of 

ammonia,  then  drop  by  drop  20  cc.  of  sodium  ammonium 

.         phosphate  (saturated  solution)  with  constant 

stirring  using  care  not  to  touch   the  bottom 

or  sides  of  the  vessel  with  the  rod.     Set  the  beaker  in  a 

cool  place  over  night,  and  in  the  morning  filter  through  a 

weighed  Gooch  crucible,  wash  with  dilute  ammonia  (i  to  3), 

dry,   ignite,  cool,  and  weigh  as    Mg2P2O7>     Multiply  this 

weight  by  2  and  then  by  0.36190  for  the  magnesia,  MgO, 

in  the  cement. 

Rapid  Method  by  Simple  Solution  in  Dilute 
Hydrochloric   A.cid 

Weigh  into  a  4  inch  casserole  0.5  gram  of  finely  ground 
dried  cement.     Add   10  cc.  of  dilute  (i  :  i)  hydrochloric 


FERRIC  OXID  AND  ALUMINA  31 

acid  and,  after  stirring  for  a  moment,  a  few  drops  of  con- 
centrated nitric  acid.  Evaporate  to  dry  ness  on  a  hot  pi  ate 
or  sand-bath,  keeping  the  dish  covered  with  a 
watch-glass  supported  upon  a  glass  triangle. 
Bake  until  all  odor  of  hydrochloric  acid  has  disappeared. 
Cool  the  casserole  slightly  and  add  20  cc.  of  dilute  hy- 
drochloric acid.  Place  the  watch-glass  tightly  upon  the 
casserole  and  stand  on  the  hot  plate  for  a  few  moments. 
Add  50  to  75  cc.  of  hot  water.  Heat  until  all  soluble  salts 
are  dissolved  and  filter.  Wash  the  residue  upon  the  filter- 
paper,  first  three  times  with  hot  water,  then  once  with  hot 
dilute  hydrochloric  acid,  and  finally  well  with  hot  water. 
Ignite  the  precipitate  (finishing  over  a  blast-lamp)  and 
weigh  as  SiO2. 

Heat  the  filtrate  from  the  SiO2  to  boiling  and  add  am- 
monia in  slight  but  distinct  excess.  Again  bring  to  the 

boiling-point  and  keep  boiling  for  a  minute 
and  Alu  or  so>  Allow  ^e  precipitated  oxids  of  iron 
mina  and  alumina  to  settle,  and  filter.  Transfer  as 

much  of  the  precipitate  as  it  is  possible  to  do 
with  a  wash-bottle  from  the  beaker  to  the  filter.  Remove 
the  filtrate  from  under  the  funnel,  and  in  its  place  stand 
the  beaker  in  which  the  precipitation  was  made.  Dissolve 
the  precipitate  by  running  hot  hydrochloric  acid  from  a 
wash-bottle  around  the  edge  of  filter-paper,  and  wash  the 
paper  free  from  yellow  color  with  water.  Reprecipitate 
the  iron  and  alumina  as  before  by  cautious  addition  of  a 
slight  excess  of  ammonia  to  the  boiling  solution.  Filter, 


32  ANALYTICAL  METHODS 

wash  with  hot  water,  ignite  and  weigh  as  ferric  oxid  and 
alumina. 

To  the  combined  filtrate  from  the  two  iron  and  alumina 
precipitations,  which  should  measure  from  300  to  400  cc.,  add 
a  few  drops  of  ammonia  and  bring  to  a  boil. 
Add  25  cc.  of  a  saturated  solution  of  ammo- 
nium oxalate  with  constant  stirring,  and  stir  and  boil  for 
a  few  minutes.  Allow  the  precipitate  to  settle  and  filter. 
Wash  with  hot  water,  and  determine  the  calcium  in  the 
precipitate  by  titration  with  standard  permanganate  as  di- 
rected on  page  40. 

Cool  the  filtrate  from  the  calcium  oxalate  precipitate, 
and  when  it  feels  thoroughly  cool  to  the  hand  add  with 
constant  stirring  20  cc.  of  a  saturated  solu- 
tion of  sodium  phosphate.  Make  strongly 
ammoniacal  with  strong  ammonia,  so  as  not  to  increase 
the  volume  unnecessarily,  and  set  aside  in  the  cold  for 
some  hours,  or  better  over  night.  Filter  and  wash  with 
a  mixture  of  i  liter  ammonia  (0.96  sp.  gr.),  2  liters  water, 
150  grams  ammonium  nitrate,  ignite,  without  drying  the 
filter-paper,  over  a  low  flame  until  the  magnesium  pyro-" 
phosphate  is  white  or  light  gray  in  color.  Cool  and 
weigh.  Multiply  the  weight  by  0.36190  for  magnesia, 
MgO. 

Mr.  Andreas  Lundtei gen,  chemist  to  the  Western  Portland 
Cement  Co.,  proceeds  thus  in  the  solution  and  evaporation 
of  the  sample.  One-half  gram  of  cement  is  carefully  moist- 
ened with  from  3  to  5  cc.  of  water  in  a  3^  inch  evaporating 


NOTES  33 

dish,  and  a  few  drops  of  nitric  acid  and  about  5  cc.  of  con- 
centrated hydrochloric  acid  added.  All  lumps  are  carefully 

crushed  with  a  glass  rod,  and  the  solution 
Modification  evaporated<  This  is  hastened  by  a  current 
of  the  Above  ,,  ,  ,  .  „  ,  ,  ,  ,,  , 

ot  hot  air  allowed  to  play  on  the  surface. 

The  air  is  heated  by  passing  through  a 
platinum  coil  placed  in  the  flame  below  the  iron  plate  on 
which  the  evaporation  is  conducted.  By  this  means  in 
from  five  to  seven  minutes  the  solution  can  be  reduced  to  a 
thick  jelly,  when  it  should  be  stirred  and  then  heated  more 
carefull}7  until  all  the  hydrochloric  acid  is  expelled. 

Notes 

After  fusing  silica  or  silicates  with  sodium  carbonate  it 
will  be  found  best  to  treat  the  fused  mass  with  hot  water 
until  it  is  thoroughly  disintegrated,  and  then  add  hy- 
drochloric acid.  The  addition  of  the  acid  first  is  likely  to 
cause  a  gelatinous  film  of  silica  to  surround  the  mass  and 
so  prevent  its  decomposition. 

Instead  of  supporting  the  watch-glass  upon  a  glass  tri- 
angle, in  rapid  evaporations,  it  may  be  held  above  the  dish 
by  three  bits  of  glass,  about  two  inches  long,  bent  at  the 
middle  to  form  a  V,  and  inverted  over  the  sides  of  the  dish. 

Some  authorities  contend  that  one  evaporation,  even 
when  the  mass  is  dried  for  many  hours,  fails  to  render  all 
the  silica  insoluble.  They  advise  moistening  the  residue 
from  the  first  evaporation  with  water  and  a  few  drops  of 
hydrochloric  acid  and  again  evaporating  to  dryness.  It  is 
essential,  however,  whether  one  or  two  evaporations  are 

3 


34  ANALYTICAL  METHODS 

made,  that  all  the  hydrochloric  acid  should  be  expelled, 
and  also  that  the  temperature  of  baking  is  not  too  high. 

Silica  is  hard  to  wash  and  retains  alkalies  tenaciously. 
It  is  well  for  the  inexperienced  operator,  until  he  finds  out 
how  much  washing  is  required,  to  test  with  silver  nitrate, 
and  continue  the  operation  until  the  washings  cease  to 
react  for  chlorids. 

Silica  may  be  ignited  wet,  but  care  must  be  taken  not 
to  dry  the  precipitate  too  quickly  over  the  flame,  else  the 
steam  in  escaping  will  carry  with  it  fine  particles  of  silica. 
The  best  plan  is  not  to  place  the  crucible  at  first  directly 
over  the  burner,  but  instead  to  one  side  of  a  low  flame. 
The  silica  must  be  ignited  over  a  blast-lamp  in  order  to 
drive  off  the  last  traces  of  water,  which  it  holds  most  tena- 
ciously. Ignition  over  a  Bunsen  burner,  even  for  some 
hours,  is  insufficient  for  complete  dehydration.  The  blast- 
lamp  will  also  help  to  burn  off  the  last  trace  of  the  car- 
bon of  the  filter-paper. 

The  purity  of  the  silica  can  easily  be  tested,  and  indeed 
in  accurate  work,  it  should  always  be  done.  After  burn- 
ing off  the  carbon,  igniting  over  a  blast  and  accurately 
weighing,  moisten  the  silica  with  dilute  sulfuric  acid  and 
then  half  fill  the  crucible  with  C.  P.  hydrofluoric  acid. 
Incline  the  crucible  on  a  tripod  over  a  burner  turned  low, 
in  such  a  way  that  the  flame  plays  under  the  upper  part 
of  the  crucible.  This  causes  a  rapid  evaporation  of  the 
solution.  When  no  more  fumes  come  from  the  crucible 
move  the  burner  back  until  it  plays  upon  the  bottom  of  the 
crucible  and  raise  the  flame  until  the  crucible  is  cherry-red. 


NOTES  35 

Cool  and  weigh.  The  loss  represents  silica,  SiO2,  and  the 
residue  in  the  crucible  is  usually  alumina.  Its  weight  may 
be  added  to  that  of  the  iron  and  alumina  found  by  pre- 
cipitation with  ammonia,  or  the  residue  may  be  dissolved 
in  concentrated  hydrochloric  acid  and  added  to  the  filtrate 
from  the  silica,  before  the  addition  of  ammonia. 

Alumina,  AlaO  ,  is  soluble  to  some  extent  in  a  large 
excess  of  ammonia.  If,  however,  the  excess  is  expelled 
by  boiling,  the  alumina  is  again  precipitated.  The  pres- 
ence of  ammonium  chlorid  in  the  solution  greatly  aids  in 
the  separation  of  alumina  by  ammonia.  The  precipitate 
of  iron  and  alumina  must  be  filtered  off  promptly  since  the 
alkaline  liquid  will  absorb  carbon  dioxid  from  the  air,  form- 
ing calcium  carbonate  which  would  be  filtered  off  with  the 
iron  and  alumina.  For  the  same  reason  when  for  any 
cause  the  filtrate  from  the  iron  and  alumina  has  to  stand 
some  days  it  should  be  acidified  with  hydrochloric  acid 
before  setting  aside.  This  is  necessary  when  the  calcium 
is  to  be  determined  volumetrically,  and  it  saves  trouble 
elsewhere,  since  the  deposit  of  calcium  carbonate  forms  as 
a  crust  on  the  sides  and  bottom  of  the  beaker,  and  is  very 
difficult  to  remove,  without  solution  and  reprecipitation. 

Magnesium  hydroxid,  Mg(OH)a,  is  not  completely  solu- 
ble in  ammonia.  The  precipitate  is,  however,  readily  sol- 
uble in  ammonia  solutions,  containing  sufficient  ammo- 
nium chlorid.  The  precipitation  of  the  magnesia  along 
with  the  iron  and  alumina  is  insured  against  by  the  for- 
mation of  ammonium  chlorid,  which  takes  place  before 
the  iron  and  alumina  are  precipitated,  on  adding  ammonia 


36  ANALYTICAL  METHODS 

to  the  hydrochloric  acid  solution.  If  preferable,  the  op- 
erator can  be  on  the  safe  side  by  adding  half  a  £ram  of  the 
salt  itself  (ammonium  chlorid)  to  the  filtrate  from  the 
silica  before  precipitating-  the  iron  and  alumina. 

The  precipitate  of  iron  and  alumina  always  contains 
more  or  less  lime  and  magnesia,  from  which  long  washing 
fails  to  free  it.  Solution  and  reprecipitation  are,  there- 
fore, necessary  to  get  around  the  difficulty.  The  precipi- 
tate is  very  apt  to  contain  traces  of  silica  also.  Some  of 
this  comes  from  the  action  of  the  ammonia  on  the  reagent 
bottle  in  which  it  is  kept,  some  from  the  action  of  the 
alkaline  liquid  in  the  beaker  in  which  the  precipitation  is 
made,  and  some  which  failed  to  be  separated  by  evapora- 
tion in  the  proper  place  is  also  carried  down  here.  Since 
the  impurity  usually  present  in  the  silica  is  alumina  and 
that  in  the  alumina  is  silica,  the  two  sources  of  error  tend 
to  balance  each  other.  If  desired  the  weighed  precipitate 
of  ferric  oxid  and  alumina  can  be  dissolved  by  fusion  with 
potassium  bisulfate  for  some  hours,  the  fused  mass  dis- 
solved in  water,  the  silica  filtered  off,  weighed,  and  the 
weight  deducted  from  that  of  the  iron  and  alumina. 

Calcium  oxalate  is  very,  insoluble  and  may  be  washed 
with  hot  water.  Some  chemists  prefer  to  add  a  little  am- 
monia to  the  wash-water,  but  to  the  author  this  seems  un- 
necessary. The  precipitate  should  always  be  formed  in  a 
boiling  ammoniacal  solution,  with  stirring,  and  allowed 
to  settle  before  filtering.  Some  chemists  heat  the  ammo- 
nium oxalate  solution  also  to  boiling  before  adding  to  the 
boiling  solution  containing  the  calcium.  Sufficient  am- 


NOTES  37 

monium  oxalate  should  always  be  added  to  convert  all  the 
magnesium  present  as  well  as  the  calcium  to  oxalate,  else 
the  precipitation  of  the  calcium  will  be  incomplete. 

The  following  is  given  as  a  quick  method  of  precipita- 
ting the  lime :  Make  the  liquid  alkaline  with  ammonia 
and  heat  it  to  boiling.  Then  take  away  the  flame  and  add 
gradually  two  grams  of  finely  powdered,  solid,  C.  P.  am- 
monium oxalate  with  constant  stirring.  Replace  the 
burner  under  the  solution  and  boil  for  a  few  minutes.  On 
taking  away,  the  precipitate  will  settle  in  a  few  minutes 
and  may  be  filtered  off  as  soon  as  it  does. 

Calcium  oxalate  on  ignition  over  a  burner  to  very  faint 
redness  changes  to  calcium  carbonate.  If  the  heating  is 
increased  and  the  blast  is  used  calcium  oxid  is  formed. 
Instead  of  weighing  as  the  oxid  some  chemists  prefer  to 
weigh  as  a  sulfate.  To  do  this,1  dry  the  precipitate  per- 
fectly, detach  it  as  far  as  possible  from  the  filter  to  a  piece 
of  black  glazed  paper.  Burn  the  filter-paper  in  a  weighed 
platinum  crucible,  and  when  all  carbonaceous  matter  is 
burned,  brush  the  precipitate  into  the  crucible  from  the 
glazed  paper.  Drop  concentrated  sulfuric  acid  on  the  pre- 
cipitate till  it  is  well  moistened,  avoiding  an  excess,  and 
heat  the  crucible  under  a  hood  cautiously,  from  a  burner 
held  in  the  hand,  until  the  swelling  of  the  mass  subsides 
and  the  excess  of  sulfuric  acid  has  been  driven  off,  as 
shown  by  the  disappearance  of  the  white  fumes  coming 
from  the  crucible.  Then  heat  for  five  minutes  to  a  cherry- 
red  heat,  but  do  not  use  the  blast.  Cool  and  weigh  as 

1  Lord:  "  Notes  on  Metallurgical  Analysis,"  p.  n. 


38  ANAL  YTICAL  METHODS 

calcium  sulfate,  which  multiplied  by  0.41185  gives  the 
equivalent  of  lime,  CaO.  The  third  scheme  above  also 
gives  a  method  of  converting  the  oxalate  to  sulfate. 

Mr.  W.  H.  Hess,  chemist  for  the  Omega  Portland  Cement 
Co.,  uses  the  following  method1  for  converting  the  calcium 
oxalate  to  calcium  sulfate.  After  burning  off  all  the  car- 
bon of  the  filter-paper,  the  crucible  is  allowed  to  cool  partly 
when  a  portion  of  chemically  pure  dry  ammonium  nitrate, 
approximately  equal  in  bulk  to  the  lime  in  the  crucible, 
and  about  twice  as  much  chemically  pure  fused  ammonium 
sulfate  are  added.  A  tight-fitting  cover  is  now  placed  on 
the  platinum  crucible  and  then  gentle  heat  is  applied.  Mr. 
Hess  found  it  very  convenient  to  incline  the  crucible  at 
an  angle  of  30°,  allowing  the  tip  of  the  crucible  cover  to 
project  outward  and  then  apply  the  flame  to  the  tip  of  the 
cover,  gradually  bringing  the  flame  under  the  crucible  as 
the  reaction  grows  less  and  less  violent.  The  reaction  is 
complete  when  fumes  of  ammonia  salts  are  no  longer 
driven  off.  Intense  ignition  is  unnecessary  and  is  to  be 
avoided.  The  crucible  should  be  weighed  with  its  cover. 

The  volumetric  method  for  determining  calcium,  given  a 
little  further  on,  also  gives  very  accurate  results. 

If,  on  evaporation  of  the  filtrate  from  the  lime,  a  white 
precipitate  settles  out,  it  should  be  redissolved  in  a  little 
hydrochloric  acid.  In  concentrating  this  filtrate  it  is  well 
to  make  acid  with  hydrochloric  acid  before  starting  the 
evaporation. 

1  J.  Am.  Chem.  Soc.,  aa,  477. 


NOTES  39 

Magnesium  pyrophosphate  is  quite  soluble  in  hot  water, 
less  so  in  cold  water,  and  practically  insoluble  in  water 
rendered  strongly  ammoniacal.  It  should  be  washed, 
therefore,  with  a  mixture  of  water  and  ammonia.  Some 
chemists  use  no  ammonium  nitrate  in  their  washing  fluid, 
and  mix  in  proportions  varying  from  ten  to  three  parts 
water  for  one  part  of  ammonia.  It  is  a  difficult  precipitate 
to  ignite  perfectly  white,  but  the  blast-lamp  should  never 
be  used  in  the  attempt  to  make  it  so,  as  destruction  of  the 
platinum  crucible  might  follow.  The  precipitate  may  be 
ignited  wet  if  a  low  flame  is  used  at  first. 

The  Gooch  crucible,  mentioned  in  one  of  the  above 
schemes,  consists  of  a  flat-bottomed,  perforated  crucible  pro- 
vided with  a  cap  (Fig.  2).  The  perforated  crucible  is  placed 
in  one  end  of  a  piece  of  soft  rubber  tub- 
ing of  large  bore,  the  other  end  of  which 

is  stretched  over  a  small  fun-  £^==)  ~~Cy 
'nel  passing  into  a  flask 
through  a  rubber  stopper  (Fig. 
3).  The  flask  is  connected 
with  the  filter  pump.  To  pre- 
pare the  filter,  pour  a  little 
prepared  asbestos  (purified  by 
washing  with  hot  concentra- 
ted hydrochloric  acid)  sus- 
pended in  water  into  the  cru- 
cible and  attach  the  suction  to  the  flask.  The  asbestos  at 
once  forms  a  thick  felt  over  the  bottom  of  the  crucible, 


40  ANALYTICAL  METHODS 

which  by  using  the  suction  may  be  readily  washed  with 
water.  After  washing,  suck  dry  as  possible  with  the  pump, 
remove  from  the  funnel,  detach  any  pieces  of  asbestos  that 
may  be  on  the  outside  of  the  bottom  of  the  crucible,  cap, 
ignite,  and  weigh.  Remove  the  cap,  attach  to  the  funnel 
as  before,  apply  the  suction  and  pour  the  liquid  to  be  fil- 
tered through  the  crucible,  wash,  cap,  dry,  if  necessary, 
ignite  and  weigh  as  before.  The  crucible  and  cap  may  be 
purchased  from  dealers  in  platinum  or  chemical  ware. 

Volumetric  Determination  of  Calcium 
Dissolve  22.56  grams  of  purtf  crystallized  potassium  per- 
manganate in  750  cc.  of  cold  distilled  water  in  a  beaker, 
cover  with  a  watch-glass  and  allow  to  stand 

°Ver  night'      In   the   morninS   filter  through 
asbestos  into  a  large  bottle  and  add  1250  cc. 

nate  '  of  distilled  water.  This  will  give  a  solution 
each  cubic  centimeter  of  which  should  be 
equivalent  to  about  o.oi  gram  of  lime  or  2.0  per  cent  when 
a  0.5  gram  sample  is  used.  To  standardize  the  solution  : 
Weigh  into  each  of  two  beakers  1.4  grams  of  pure  crystal- 
lized ferrous  ammonium  sulfate,  add  cold  water,  allow  the 
salt  to  completely  dissolve  without  stirring  and  then  add 
10  cc.  of  dilute  sulfuric  acid.  Stir  and  run  in  the  per- 
manganate from  a  burette  until  the  color  of  the  solution 
in  the  beaker  just  changes  to  pink.  The  weight  of  the 
double  salt  used  divided  by  14,  and  then  by  the  number  of 
cubic  centimeters  of  permanganate  required,  will  give  the 
lime,  CaO,  value  per  cubic  centimeter  for  the  permanga- 


NOTES  41 

nate.  The  duplicate  titrations  shcmld  check  closely  ;  if 
not,  another  pair  should  be  run.  For  other  methods  of 
standardizing  the  permanganate  solution  see  ' '  Determina- 
tion of  Ferric  Oxid." 

Precipitate  the  silica  and  the  iron  and  alumina  in  the 
usual  way.     Heat  the  filtrate  to  boiling,  add  25  cc.  of  sat- 
urated ammonium  oxalate  solution,  stir  well, 
Determma- 

and  alter  removing  the  beaker  from  the  source 

of  heat,  allow  the  precipitate  to  settle.  Filter 
and  wash  well  with  hot  water.  Now  punch  a  hole  in  the 
bottom  of  the  filter-paper  and  wash  as  much  as  possible  of 
the  precipitate  into  a  large  beaker,  flask  or  porcelain  dish. 
Wash  the  filter-paper  with  small  quantities  of  hot  dilute 
sulfuric  acid  from  a  wash-bottle,  and  then  well  with  hot 
water.  Dilute  the  solution  to  300  or  400  cc.,  add  10  cc.  of 
dilute  sulfuric  acid  and  warm  to  60°  or  70°  C.  When  all 
the  precipitate  has  dissolved  titrate  the  solution  with  the 
standard  permanganate.  Multiply  the  number  of  cubic 
centimeters  of  permanganate  required  by  the  lime  value  of 
the  standard  solution  and  divide  the  product  by  the  weight 
of  cement  taken  for  a  sample.  The  result  multiplied  by 
100  will  be  the  per  cent  of  lime,  CaO,  in  the  cement. 

Notes 

The  method  depends  upon  the  reaction  between  oxalic 
acid  and  potassium  permanganate. 
5H2C2O4  +  2KMnO4  +  3H2SO4  = 

ioC02  -f  K2S04  +  2MnS04  +  8H2O 


42  ANALYTICAL  METHODS 

The  reaction  between  iron  and  permanganate  is 

ioFeSO4  +  2KMnO4  +  8H2SO4  = 

5Fe2(SO4)3  +  2MnSO4  +  K2SO4  +  8H2O. 

Hence  5  molecules  H2C2O4  =  2  mols.  KMnO4  =  loniols. 
FeSO4  or  5  mols.  H2C2O4  (=  5  mols.  CaO)=  10  mols.  FeSO4 
(=10  atoms  Fe). 

Then  5  mols.  CaO  =  10  atoms  Fe,  and  5(40  +  16)  CaO 
=  jo  X  56  Fe,  or  280  CaO  =  560  Fe. 

Hence,  CaO    :  Fe  ::    280   :   560,    from  which    CaO   = 


So  the  iron  value  of  any  permanganate  solution  divided 
by.  2  will  give  its  lime  value. 

Instead  of  punching  a  hole  in  the  filter-paper  some  ope- 
rators prefer  to  dissolve  the  precipitate  in  very  dilute  hy- 
drochloric acid,  using  as  small  a  quantity  as  possible  ; 
washing  the  paper  thoroughly  with  hot  water  and,  after 
adding  some  sulfuric  acid  and  heating  to  60°  C.,  titrating 
with  permanganate.  Provided  the  quantity  of  hydro- 
chloric acid  used  for  solution  is  kept  small  the  results  will 
be  perfectly  accurate  and  probably  time  can  be  saved  by 
proceeding  thus. 

Volumetric  Determination  of  Magnesium 

Dissolve  12.29  grams  of  pure  arsenious  acid,  AsaO3,  in 
nitric  acid,  avoiding  a  large  excess.  Evaporate  todryness 
on  a  water-bath  and  neutralize  with  sodium  carbonate 


DE  TERM  IN  A  TION  OF  MA  GNESIUM  43 

after  dissolving  the   residue  in  a  little  water.     Pour  the 

solution  into  a  graduated  liter  flask  and  after 

Standard         rinsing  Out  the  dish  into  this  latter  dilute 

to  the  mark.  Each  cubic  centimeter  of  this 
Arsenate.  .  . 

solution  is  equivalent  to  0.005  gram  of  mag- 
nesia, MgO. 

Dissolve  49.314  grams  of  pure  crystallized  sodium  thio- 
sulfate  in   2000  cc.  of  water.     One  cc.    of   this   solution 
should  be  equivalent  to  0.002  gram  of  mag- 
Standard         nesia,  MgO.     To  standardize,  measure  with 
o  mm  a  pjpette   I0  cc   Q£  tjje  standard  sodium  arse- 

nate  solution  into  a  small  beaker  or  dish,  add  3 
to  5  grams  of  potassium  iodid  and  25  cc.  of  hydrochloric  acid 
(sp.  gr.  1. 10)  and  without  diluting  titrate  with  the  standard 
thiosulfate  until  the  liquid  is  colorless.  It  is  not  necessary 
to  add  starch  as  an  indicator  as  the  end  reaction  is  clear 
enough  without  it  and  the  change  from  pale  straw  color 
to  colorless  is  sudden  and  perfectly  distinct.  Since  10  cc. 
of  the  arsenate  solution  represents  0.05  gram  of  magnesia, 
0.05  divided  by  the  number  of  cubic  centimeters  of  thio- 
sulfate required  will  give  the  magnesia,  MgO,  value  per 
cubic  centimeter  of  the  standard  thiosulfate. 

Separate  the  silica,  iron  and  alumina,  and  lime,  in  the 
usual  manner,  taking  care,  however,  to  use  only  a  slight 
Th  D  excess  of  ammonium  oxalate  in  precipitating 

the  lime.  Place  the  filtrate  from  the  calcium 
mination. 

oxalate  m  a  large  Erlenmeyer  flask  or  a  gas- 
bottle  of  sufficient  capacity.  Add  one-sixth  the  volume 


44  ANALYTICAL  METHODS 

of  the  liquid  of  strong  ammonia  and  50  cc.  of  a  10  per  cent 
solution  of  sodium  arsenate.  Cork  up  tightly  and  shake 
vigorously  for  ten  minutes.  Allow  the  precipitate  to  set- 
tle somewhat  and  wash  with  a  mixture  of  three  parts 
water  and  one  part  strong  ammonia  until  the  washings 
cease  to  react  for  arsenic.  Avoid  using  an  excess  of  wash- 
ing fluid,  however.  Dissolve  the  precipitate  in  dilute  hy- 
drochloric acid  (i  :  i)  allowing  the  acid  solution  to  run 
into  the  flask  in  which  the  precipitation  was  made  and 
wash  the  filter-paper  with  dilute  acid  until  the  washings 
and  solution  measure  75  to  100  cc.  Cool  if  not  already  so 
and  add  from  3  to  5  grams  of  potassium  iodid,  free  from 
iodate,  allow  the  solution  to  stand  a  few  minutes  and  ti- 
trate with  the  standard  thiosulfate  until  the  color  of  the 
liberated  iodin  fades  first  to  a  pale  straw  color,  and  then 
disappears  altogether. 

Notes 

This  method  depends  upon  the  fact  that  magnesium  can 
be  entirely  precipitated  from  strongly  ammoniacal  solu- 
tion as  magnesium  ammonium  arsenate  bv  addition  of  so- 
dium arsenate.  The  arsenic  is  then  determined  volumet- 
rically  and  from  this  the  magnesium  calculated. 

From  the  formula  of  the  double  salt,  Mg2(NH4)2As2O8  -+- 
H2O,  it  will  be  seen  that  one  atom  of  arsenic,  As,  is  equiv- 
alent to  one  of  magnesia,  MgO,  and  consequently  the 
ratio  of  magnesia  to  arsenious  acid,  As2O3,  is  2(24.28  -f 
16)  :  (75.01  X  2  +  16  X  3)  or  80.56  :  198.02,  from  which 
MgO  =  0.4068  X  AsaO3. 


NOTES  45 

When  a  solution  of  arsenic  acid  contains  sufficient  sul- 
furic  or  hydrochloric  acid,  the  arsenic  is  quickly  reduced 
from  the  higher  to  the  lower  state  of  oxidation  even  in  the 
cold,  according  to  the  reaction 

As205  +  4KI  +  4HC1  =  As203  +  sKCl  +  2H2O  +  2l2. 
The  liberated   iodin  is  titrated  with  thiosulfate  when  the 
following  reaction  takes  place : 

2Na2S,03  +  I2  =  2NaI  +  Na2S4O8. 

On  adding  the  potassium  iodid  to  the  acid  solution  a 
brown  precipitate  forms  which,  however,  disappears  when 
the  thiosulfate  is  added.  The  complete  reduction  of  the 
arsenic  only  takes  place  in  very  acid  solutions,  hence  the 
precipitate  of  magnesium  ammonium  arsenate  should  be 
dissolved  in  and  the  filter-paper  washed  with  dilute  hydro- 
chloric acid  (i  :  i).  The  precipitate  of  magnesium  ammo- 
nium arsenate  is  less  soluble  when  an  excess  of  sodium 
arsenate  is  present  in  the  ammoniacal  solution.  It  is  more 
soluble  when  a  large  excess  of  ammonium  oxalate  has 
been  used  to  precipitate  the  lime ;  consequently  guard 
against  adding  much  more  ammonium  oxalate  than  is 
necessary  to  entirely  precipitate  the  lime  and  add  a  con- 
siderable excess  of  sodium  arsenate  in  precipitating  the 
magnesia.  The  precipitate  must  be  washed  with  dilute 
ammonia  as  it  is  soluble  in  water  and,  as  it  is  not  entirely 
insoluble  in  aminonia,  the  volume  of  the  washing  fluid 
should  be  kept  as  small  as  possible. 

Agitation  greatly  hastens  the  precipitation  of  the  mag- 
nesia. An  ordinary  "milkshake"  apparatus  will  be  found 


46 


ANALYTICAL  METHODS 


Fig.  4. 


NOTES  47 

very  convenient  for  shaking,  if  provided  with  an  arrange- 
ment for  holding  the  flasks  (see  Fig.  4).  The  precipitate 
is  very  heavy  and  settles  rapidly. 

Instead  of  standardizing  the  solution  against  a  standard 
solution  of  sodium  arsenate,  bichromate  or  permanganate, 
whose  iron  value  is  known,  may  be  used.  Measure  into  a 
beaker  from  a  burette  such  a  quantity  of  standard  bichro- 
mate or  permanganate  as  is  equivalent  to  0.1389  gram  of 
metallic  iron,  add  a  little  dilute  sulfuric  acid  and  i  gram 
of  potassium  iodid  and  titrate  with  the  standard  thiosul- 
fate  until  the  yellow  color  almost  fades,  then  add  a  little 
boiled  starch  solution  and  titrate  until  the  blue  color  of 
the  starch  entirely  disappears.  0.1389  gram  of  metallic 
iron  is  equivalent  to  0.05  gram  of  magnesia.  To  find  the 
magnesia  value,  therefore,  of  the  thiosulfate  divide  0.05 
by  the  number  of  cubic  centimeters  of  thiosulfate  required. 
The  calculation  is  explained  as  follows : 

(I).  K2Cr207  +  6KI  +  I4HC1  =  8KC1  +  Cr2Cl6  +  7H2O  +  61 
(II).  K2Cr207  +  6FeCl  +  I4HC1  =  2KC1  +  Cr2Cl6  +  7H2O  + 

3Fe2Cl6. 

(III).  As.,05  +  4KI  +  4HC1  =  As-A  -f  4KC1  +  2H2O  +  4!. 
From  (I)  and  (II)  6  atoms  I  =  i  mol.  K2CrjO7  =  6  atoms  Fe. 
From  (III)  i  atoms  As  =  4  atoms  I. 

i  atom  As  —  i  mol.  MgO  =  2  atoms  I. 
3  mols.  MgO  =  6  atoms  1  =  6  atoms  Fe. 
3(24.3  +  16)  MgO  =  120.9  MgO  =  6  X  56  Fe  =  336  Fe. 
120.9  :  336  :  :  °-°5  '-x        x  =  0.1389. 


48  ANALYTICAL  METHODS 

Rapid  Determination  of  Silica  and  Lime  in 
Cement 

It  is  frequently  desirable  to  know  the  percentage  of 
silica  and  lime  present  in  a  cement  without  regard  to  the 
ferric  oxid  and  alumina  and  the  magnesia.  The  follow- 
ing rapid  method,  communicated  to  the  author  by  Mr. 
Andreas  L,undteigen,  chemist  of  the  Western  Portland 
Cement  Co.,  Yankton,  S.  D.,  is  designed  to  meet  this  end. 

Carefully  moisten  0.5  gram  of  cement  with  from  3  to  5 
cc.  of  water  in  a  2/4  incn  evaporating  dish  or  casserole. 
Add  5  cc.  of  concentrated  hydrochloric  acid  and  a  few 
drops  of  nitric  acid  and  carefully  crush  all  lumps  with  a 
glass  rod.  Evaporate  the  solution  quickly  on  a  hot  plate 
by  allowing  a  current  of  hot  air  to  play  upqn  its  surface 
(see  page  32).  In  from  five  to  seven  minutes  the  contents 
of  the  dish  will  have  become  a  stiff  jelly.  Stir  this  in 
order  to  make  the  silica  granular  and  easier  to  filter,  and 
heat  the  dish  more  carefully  until  all  the  hydrochloric 
acid  is  expelled.  Redissolve  the  residue  in  hydrochloric 
acid  and  water,  filter,  ignite  and  weigh  the  silica,  SiO2,  as 
usual. 

Dilute  the  filtrate  to  250  cc.,  bring  to  a  boil  and  add 
enough  ammonia  to  precipitate  all  the  iron  and  alumina. 
Again  bring  to  a  boil,  and  while  in  this  condition,  add 
oxalic  acid  solution,  drop  by  drop,  until  the  red  color  of  the 
iron  has  disappeared,  then  precipitate  the  lime  by  adding 
an  excess  of  ammonium  oxalate.  Allow  to  settle,  filter, 
wash  and  determine  by  titration  with  standard  potassium 
permanganate  as  described  on  page  40. 


DETERMINATION  OF  FERRIC  OXID  49 

Determination  of  Ferric  Oxid 

By  Titration  with  Potassium  Bichromate 

(Penny's  Method) 

Place  from  10  to  15  grams  of  C.  P.  potassium  bichromate 
in  a  sufficiently  large  platinum  crucible.  Heat  carefully, 
avoiding  all  contact  of  the  flame  with  the 
Potassium  contents  of  the  crucible,  until  the  salt  just 
g-  ,  t  fuses  to  a  dark  liquid.  Then  withdraw  at 

once  from  the  flame  and  let  the  crucible  cool. 
Weigh  3.074  grams  of  the  fused  bichromate,  which  in 
cooling  will  have  crumbled  to  a  powder,  dissolve  in  250 
to  300  cc.  of  cold  water  and  pour  into  a  liter  graduated 
flask.  Rinse  out  the  beaker  several  times  into  the  flask 
and  dilute  the  solution  to  the  liter  mark.  Mix  well.  One 
cc.  of  this  solution  should  be  equivalent  to  0.005  gram  of 
ferric  oxid,  Fe2O3. 

To  test  or  standardize  the  solution,  weigh  into  a  small 
beaker  0.4900  gram  of  pure  ferrous  ammonium  sulfate 
(equivalent  to  o.i-gram  of  ferric  oxid).  Dissolve  in  50  cc. 
of  water  and,  when  all  the  salt  is  in  solution,  add  5  cc.  of 
dilute  hydrochloric  acid.  Run  the  bichromate  solution 
from  a  burette  into  the  liquid  in  the  beaker  until  a 
drop  of  the  iron  solution  placed  upon  a  white  porcelain 
plate  and  mixed  by  stirring  with  a  drop  of  a  freshly  made 
i  per  cent  solution  of  potassium  ferricyanid  no  longer  as- 
sumes a  blue  color,  but  instead  gives  a  yellow.  This 
should  require  20  cc.  of  the  bichromate  solution.  If  more 
or  less,  repeat  the  test,  and  if  the  first  and  second  results 


5o  ANALYTICAL  METHODS 

agree,  divide  o.  i ,  the  ferric  oxid  equivalent  of  the  weight 
of  the  ferrous  ammonium  sulfate  used,  by  the  number  of 
cubic  centimeters  of  bichromate  required.  The  result  will 
give  the  ferric  oxid  equivalent,  or  value,  in  grams  for 
each  cubic  centimeter  of  the  standard  potassium  bichro- 
mate. 

Some  operators  prefer  to  standardize  their  bichromate 
against  iron  wire.  In  this  case  clean  o.i  gram  of  fine  iron 
wire  by  rubbing  between  fine  emery  paper  and  then  be- 
tween filter-paper.  Coil  around  a  lead  pencil  and  weigh. 
Drop  the  coil  in  a  small  beaker,  add  20  cc.  of  dilute  hy- 
drochloric acid  and  heat  until  all  the  wire  dissolves. 
Wash  down  the  sides  of  the  beaker  with  a  wash-bottle, 
bring  the  contents  to  a  boil  and  drop  in  the  stannous 
chlorid  solution,  described  below,  slowly  until  the  last  drop 
turns  the  solution  colorless.  Remove  from  the  source  of 
heat  and  cool  the  liquid  rapidly  by  setting  the  dish  in  a 
vessel  of  cold  water.  When  nearly  cold  add  at  once  15 
cc.  of  saturated  mercuric  chlorid  solution,  and  stir  well. 
Allow  to  stand  a  few  minutes  and  titrate  with  the  bichro- 
mate as  described  above.  Multiply  the  weight  of  the  iron 
wire  by  0.003  an<i  deduct  this  from  the  original  weight, 
for  impurities  in  the  wire.  The  corrected  weight  divided 
by  0.7  and  then  by  the  number  of  cubic  centimeters  of  bi- 
chromate required,  gives  the  ferric  oxid  equivalent  in  grams 
to  each  cubic  centimeter  of  the  standard  bichromate.  This 
value  should  be  checked  unless  within  the  limits  of  allow- 
able error  to  0.005  gram. 


DETERMINA  TION  OF  FERRIC  OXID  51 

Dissolve  100  grams  of  stannous  chlorid  solution  in  a 
mixture  of  300  cc.  of  water  and  100  cc.  of  hydrochloric 
acid.  Add  scraps  of  metallic  tin  and  boil  un- 
Stannous  n  h  soiution  is  ciear  and  colorless.  Keep 
Chlorid  So- 
lution solution  in  a  closely  stoppered  bottle 

(best  a  dropping  bottle)  containing  metallic 
tin.  This  solution  should  be  kept  from  the  air. 

Make  a  saturated  solution  of  mercuric  chlorid  by  put- 
ting an   excess  of  the  salt  in  a  bottle  and 
MgCLSol.      _„?  .,, 

filling  up  with  water  and  shaking  as  the  so- 
lution gets  low. 

Weigh  i  gram  of  finely  ground  cement  into  a  small 
beaker  and  add  15  cc.  of  dilute  hydrochloric  acid,  heat 

from  ten  to  fifteen  minutes  and  add  a  little 
mination  "  water-  Heat  to  boiling  and  filter  through  a 

small  filter,  washing  the  residue  well  with 
water  and  catching  the  filtrate  and  washings  in  a  porcelain 
dish.  Add  to  the  solution  5  cc.  of  dilute  hydrochloric 
acid  and  bring  to  a  boil.  Add  carefully,  drop  by  drop,  the 
stannous  chlorid  solution  until  the  last  drop  makes  the 
solution  colorless.  Remove  from  the  burner  and  cool  the 
liquid  by  setting  in  a  vessel  of  cold  water.  When  nearly 
cold  add  15  cc.  of  the  mercuric  chlorid  solution  and  stir 
the  liquid  in  the  dish  with  a  glass  rod.  Allow  the  mix- 
ture to  stand  for  a  few  minutes,  during  which  time  a  slight 
white  precipitate  should  form.  Run  in  the  standard  bi- 
chromate solution  carefully  from  a  burette  until  a  drop  of 
the  iron  solution  tested  with  a  drop  of  i  per  cent  solu- 


52  ANALYTICAL  METHODS 

tion  of  potassium  ferricyanid  no  longer  shows  a  blue,  but 
instead  a  yellow  color.  Multiply  the  number  of  cubic 
centimeters  of  bichromate  used  by  the  ferric  oxid  equiva- 
lent per  cubic  centimeter  of  the  bichromate  and  divide  the 
product  by  the  weight  of  the  sample.  The  result  multi- 
plied by  100  gives  the  per  cent  of  the  ferric  oxid,  Fe2O3,  in 
the  cement. 

Notes 

Treatment  with  hydrochloric  acid  is  sufficient  to  dis- 
solve all  except  a  mere  trace  of  iron  in  Portland  cement. 

A  strongly  acid  solution  of  ferric  chlorid,  if  boiling  hot, 
is  instantly  reduced  to  ferrous  chlorid  by  a  solution  of 
stannous  chlorid  according  to  the  following  reaction  : 

Fe2Cl6  +  SnCl2  =  SnCl4  -f-  2FeCl2. 

The  operator  can  tell  when  complete  reduction  has  taken 
place  by  the  disappearance  of  the  yellow 'color  of  the  solu- 
tion. The  excess  of  stannous  chlorid  is  removed  by  addi- 
tion of  mercuric  chlorid  when  the  following  takes  place ; 

SnCl,  +  2HgCl,  =  SnCl4  +  Hg2Cl2. 

The  precipitate,  Hg2Cl2,  should  be  white  ;  if  colored  gray 
too  much  stannous  chlorid  was  used  in  reduction  and  mer- 
cury has  been  formed.  As  mercury  reacts  with  the  bichro- 
mate, when  the  precipitate  formed  on  adding  mercuric 
chlorid  is  not  perfectly  white,  but  is  colored  gray,  the  de- 
termination should  be  repeated,  using  more  care  to  avoid 
a  large  excess  of  the  tin  solution.  If  no  precipitate  is 
formed  on  addition  of  mercuric  chlorid,  the  stannous 


DETERMINATION  OF  FERRIC  OXID          53 

chlorid  has  not  been  added  in  excess,  and  all  the  iron  will 
not  have  been  reduced  to  the  ferrous  state. 

Ferrous  salts  are  oxidized  to  ferric  compounds  by  bichro- 
mate when  in  a  solution  containing  a  considerable  excess 
of  hydrochloric  or  sulfuric  acid.     The  reaction  is : 
6FeCl2  +  K2Cr207  +  I4HC1  =  3Fe2Cl6  +  Cr2Cl6  +  2KC1  +  7H2O 

The  ferrous  ammonium  sulfate  has  the  formula  Fe(NH4)2 
(SO4)2.6H2O.  It,  therefore,  contains  one-seventh  its  weight 
of  iron  and  is  equivalent  to  0.20408  of  its  weight  of  ferric 
oxid,  Fe2O3. 

To  make  a  i  per  cent  solution  of  potassium  ferricyanid, 
dissolve  i  gram  of  the  salt  in  100  cc.  of  water.  Ferric 
compounds  give  a  yellow  color  to  this  solution,  while  fer- 
rous compounds  impart  an  intense  blue  color.  This  solu- 
tion must  always  be  made  up  fresh  as  it  is  reduced  b3'  ex- 
posure to  light. 

By  Titration  with  Potassium  Permanganate 

(Marguerite's  Method) 

Dissolve  1.975  grams  of  pure  cry stall ized  potassium  per- 
manganate in  a  liter  of  water,  allow  to  stand  all  night  and 
in  the  morning  filter  through  asbestos  into  a 

Standard        Bottle.     To  test,  or  standardize,  the  solution, 

Potassium  .        . 

p  weigh  into  each  ot  two  beakers  0.4900  gram 

nate.  °^  Pure  ferrous  ammonium  sulfate,  equivalent 

to  o.  i  gram  of  ferric  oxid,  Fe2O3.  Dissolve  in 
50  cc.  of  water,  without  heating,  add  10  cc.  of  dilute  sul- 
furic acid  and  run  in  the  permanganate  from  a  burette  un- 


54  ANALYTICAL  METHODS 

til  the  color  of  the  solution  in  the  beaker  just  begins  to 
turn  pinkish.  Take  the  reading  of  the  burette  and  then 
add  another  drop,  which  should  cause  the  solution  to  be- 
come decidedly  pinkish.  Divide  the  weight  of  ferric  oxid 
(o.i  gram)  equivalent  to  the  weight  of  ferrous  ammonium 
sulfate  taken  for  the  titration  (0.49  gram)  by  the  number 
of  cubic  centimeters  of  permanganate  required  ;  the  result 
will  give  the  ferric  oxid  equivalent  to  i  cc.  of  the  per- 
manganate. 

To  use  iron  wire  in  standardizing,  clean  two  pieces  of 
fine  iron  wire,  weighing  o.i  gram  each,  by  rubbing  first 
between  emery  paper  and  then  with  a  cloth.  Coil  around 
a  lead  pencil  and  weigh  each  coil.  Put  30  cc.  of  dilute 
sulfuric  acid  in  a  strong  gas  bottle  provided  with  a  per- 
forated stopper  through  which  passes  a  perfect  fitting  glass 
tube  with  a  hole  blown  in  its  side  (Fig.  5).  Heat  the  acid 
to  boiling  and  drop  in  a  coil  of  wire.  When 
the  solution  of  the  latter  is  complete,  remove 
the  bottle  from  the  source  of  heat  and,  after 
closing  the  opening  by  pushing  the  perforated 
glass  tube  down  until  its  opening  is  closed 
by  the  stopper,  allow  the  gas-bottle  to  cool. 
'Fi  When  cold  titrate  the  solution  with  the  per- 

manganate solution  as  above.  Multiply  the 
weight  of  the  iron  wire  by  0.003  and  deduct  the  result 
from  the  original  weight  for  impurities.  Multiply  the 
corrected  weight  by  1.4286,  or  divide  by  0.7,  and  divide 
by  the  number  of  cubic  centimeters  of  permanganate 


DETERMINATION  OF  FERRIC  OXID  55 

required.  The  result  will  be  the  ferric  oxid  equivalent 
of  i  cc.  of  the  standard  potassium  permanganate.  Re- 
peat the  test  with  the  other  weighed  coil  of  iron  wire.  The 
values  for  each  cubic  centimeter  of  permanganate  by  the 
two  titrations  should  agree  closely.  Yet  another  way  is 
to  dissolve  the  iron  wire  in  15  cc.  of  dilute  sulfuric  acid 
in  a  beaker,  cool,  dilute,  pass  through 
the  reductor,  and  titrate  with  the  per- 
manganate, calculating  the  results  as 
above. 

The  following   ' '  simplified  reductor  ' ' 
is  the  design  of  Dr.  Porter  W.  Shimer,  of 

Lafayette  College.       His  de- 
Apparatus. 

scnption  of  the  apparatus1  is 

as  follows :  ' '  The  reductor  tube  (Fig.  6) 
is  a  plain  glass  tube,  three-eighths  inch 
internal  diameter,  drawn  out  and  cut  off 
at  its  lower  end.  It  is  filled  by  placing^, 

a  few  small  pieces  of  broken  glass  in  the   ^^     

drawn-out  portion,  and  on  this  about  an         — ' 
inch  of  well  cleaned  sand.     The  tube  is 
then  filled  with  amalgamated  zinc  of  as 
nearly  uniform  twenty  mesh  size  as  pos- 
sible.   About  80  grams  are  required.     No 
asbestos  or  glass  wool  is  used.     The  sand 
prevents   particles   of   zinc  from  falling 
through  and  it  does  not  become  clogged  by  use.     *    *    * 
The  consumption  of  zinc  is  very  small,  and  when  the  column 

1  J.  Am.  Chem.  Soc.,  ai,  723. 


56  ANALYTICAL  METHODS 

has  settled  about  an  inch  a  little  fresh  zinc  can  easily  be 
poured  in  from  above.  The  reductor  tube  is  united  with  a 
4  inch  funnel  by  means  of  rubber  tubing,  well  tightened 
with  wire.  Between  the  funnel  and  reductor  is  a  Hoffman 
clamp.  The  lower  end  of  the  tube  passes  through  a  soft 
two-hole  stopper  so  far  as  to  reach  half  way  to  the  bottom 
of  a  heavy-walled  pint  gas-bottle.  The  gas-bottle  is  con- 
nected with  a  filter-pump  through  an  intermediate  safety 
bottle  and  valve.  The  funnel  is  clamped  to  a  retort  stand  in 
such  a  manner  as  to  allow  the  tube  and  gas-bottle  to  swing 
easily  in  all  directions.  It  is  well  to  adjust  the  height  so  as 
to  leave  the  gas-bottle  raised  slightly  above  the  base.  The 
passage  of  the  suction  through  the  reductor  may  be  effected 
either  by  use  of  the  pump  or  by  means  of  the  vacuum  ob- 
tained by  condensation  of  steam,  devised  originally  in  Bun- 
sen 's  laboratory.  In  using  the  latter  method  a  little  water 
ma}r  be  boiled  in  the  gas-bottle  until  all  air  is  expelled,  and 
then  quickly  unite  with  the  reductor,  the  clamp  on  the 
filter-pump  being  closed.  The  speed  of  filtration  is  regu- 
lated by  the  xipper  clamp.  Instead  of  filling  the  gas-bottle 
with  steam  by  boiling  water  in  it,  it  is  better  to  have  a 
convenient  tin  or  copper  can  containing  boiling  water  and 
provided  with  one  or  more  short  steam  outlet  tubes  on  top. 
The  empty  gas-bottle  is  inverted  over  one  of  these  steam 
outlets  and,  when  filled  with  live  steam,  is  taken  off  and 
united  as  quickly  as  possible  with  the  reductor.  This 
latter  method  has  the  advantage  of  starting  with  an  empty 
gas-bottle  which  is  desirable  on  the  score  of  accuracy  both 
in  iron  and  phosphorus  determinations." 


DETERMINA TION  OF  FERRIC  OXID  57 

To  use  the  reductor  first  pass,  by  the  aid  of  suction, 
about  50  cc.  of  cold  dilute  sulfuric  acid  (i  part  acid  to 
20  parts  of  water)  through  the  reductor,  and  then  follow 
with  200  cc.  of  cold  distilled  water.  The  Hoffman  clamp 
should  be  closed  before  all  the  water  has  run  out  of  the 
funnel  so  as  to  keep  the  tube  full  of  water.  Now  empty 
the  flask,  again  attach  to  the  tube,  pour  the  iron  solution 
into  the  funnel  and  open  the  clamp.  Just  before  the  fun- 
nel becomes  empty,  run  water  around  its  sides  and  rinse 
the  beaker  well  with  water,  running  the  washings  also 
through  the  reductor,  using  about  100  to  150  cc.  of  water 
to  wash  the  funnel  and  beaker.  The  time  required  for  the 
iron  solution  to  filter  through  the  zinc,  should  be  regulated 
by  the  upper  clamp  to  occupy  from  three  and  a  half  to 
five  minutes. 

Weigh  i  gram  of  finely  ground  cement  into  a  beaker 
and  add  15  cc.  of  hydrochloric  acid.  Heat  for  ten  to  fifteen 

minutes,  add  200  cc.  of  water  and  heat  to 
nation  boiling.  Add  ammonia  in  slight  but  distinct 

excess,  boil  a  few  minutes,  allow  the  precipi- 
tate to  settle,  filter,  using  the  filter-pump  if  one  is  at 
hand,  and  wash  two  or  three  times  with  hot  water.  Place 
a  clean  flask  under  the  funnel  and  redissolve  the  precipitate 
in  a  mixture  of  15  cc.  dilute  sulfuric  acid,  60  cc.  water, 
made  up  in  the  beaker  in  which  the  precipitation  was 
effected.  Wash  the  filter  and  silica  free  from  iron  with 
cold  water,  pass  through  the  reductor  and  titrate  the  solu- 
tion with  permanganate.  Multiply  the  number  of  cubic 


58  ANALYTICAL  METHODS 

centimeters  of  standard  permangaante  required  by  the  ferric 
oxid  value  of  the  permanganate  and  then  by  100.  Divide 
the  result  by  the  weight  of  cement  taken  ;  the  quotient 
will  be  the  per  cent  of  ferric  oxid,  Fe2O3,  in  the  cement. 

Notes 

Ferrous  salts  are  oxidized  by  potassium  permanganate 
in  solutions  containing  free  acid  to  ferric  salts  according  to 
the  reaction, 
ioFeS04  +  2KMn04  +  8H2SO4  = 

5Fe2(SO4)3  +  K2SO4  +  2MnSO4  -f  8H2O. 
Potassium  permanganate  does  not  give  trustworthy  results 
in  the  presence  of  free  hydrochloric  acid.  Owing  to  its 
liability  to  be  changed  by  light  and  with  time,  it  should 
be  kept  in  the  dark  and  restandardized  ever}'  few  months. 

Instead  of  reducing  the  iron  solution  by  means  of  a  re- 
ductor,  the  gas-bottle,  mentioned  on  page  54,  may  be  used. 
Pour  the  solution  into  the  bottle.  Add  i  gram  of  granu- 
lated zinc,  stopper  and  allow  to  stand  until  the  evolution 
of  hydrogen  slackens ;  then  heat  to  boiling.  When  the 
zinc  is  completely  dissolved  (it  may  be  necessary  to  add 
more  acid  to  effect  this),  push  down  the  glass  tube,  cool, 
and  after  adding  10  cc.  of  dilute  sulfuric  acid  titrate  with 
the  permanganate. 

If  desired  the  residue  left  on  dissolving  the  ferric  oxid 
and  alumina  in  sulfuric  acid  may  be  ignited  to  destroy  the 
filter-paper,  moistened  with  dilute  sulfuric  acid,  and  then 
dissolved  in  hydrofluoric  acid.  This  latter  may  then  be 


DE  TERMINA  TION  OF  SULFUR  1C  A CID        59 

gotten  rid  of  by  evaporation  until  sulfuric  acid  fumes  begin 
to  come  from  the  crucible.  The  residual  liquid  is  to  be 
washed  into  the  solution  of  the  ferric  oxid  and  alumina, 
and  the  whole,  after  reduction,  titrated  with  standard  per- 
manganate. 

If  the  iron  were  determined  in  cement  as  in  iron  ores  by 
dissolving  in  dilute  hydrochloric  acid  and  evaporating 
with  sulfuric  acid  until  the  former  has  been  expelled,  cal- 
cium sulfate  would  be  formed.  This  would  fail  to  entirely 
dissolve  on  diluting  with  water  and  would,  on  attempting 
to  free  the  iron  solution  from  the  insoluble  matter,  clog 
up  the  filter-paper  making  a  tedious  filtration.  The 
method  given  is  much  more  satisfactory  and  saves  time. 

Determination  of  Sulfuric  Acid 
By  Solution  in  HC1 

Weigh  i  gram  of  finely  ground  dried  cement  into  a  cas- 
serole or  dish  and  add  15  cc.  of  dilute  hydrochloric  acid 
and  5  cc.  of  concentrated  nitric  acid.  Evaporate  the  solu- 
tion to  dryness  and  heat  until  all  odor  of  hydrochloric 
acid  has  disappeared  from  the  contents  of  the  dish.  Cool, 
add  5  cc.  of  hydrochloric  acid  and  heat  fora  few  moments, 
then  add  50  cc.  of  hot  water,  digest  a  little  while  and  filter 
off  the  silica.  Heat  the  filtrate  from  the  silica  to  boiling 
and  add  10  cc.  of  boiling  10  per  cent  barium  chlorid  solu- 
tion. Stir  well  and  allow  to  stand  over  night.  Filter, 
ignite,  and  weigh  as  BaSO4,  which  multiplied  by  0.34291 
gives  SO3,  or  by  0.58565,  gives  calcium  sulfate,  CaSO4.  In 
this  latter  case  multiply  the  percentage  of  calcium  sulfate 


60  ANALYTICAL  METHODS 

by  0.41185  and  deduct  from  the  percentage  of  lime  for  the 
true  percentage  of  calcium  oxid,  CaO. 

By  Fusion  with  Na2CO3  and  KNO3 

Place  i  gram  of  cement,  finely  ground  and  dried,  in  a 
large  platinum  crucible  and  thoroughly  mix  it  by  stirring 
with  6  grams  of  sodium  carbonate  and  a  little  sodium  or 
potassium  nitrate.  Heat  the  mixture,  gently  at  first, 
over  a  Bunsen  burner  for  a  while  and  then  over  a  blast- 
lamp  until  the  contents  of  the  crucible  are  in  quiet 
fusion.  Run  the  fused  mass  well  up  on  the  sides  of  the 
crucible  and  chill  by  dipping  the  bottom  of  the  crucible  in 
a  vessel  of  cold  water.  If  loose,  remove  the  mass  from 
the  crucible  to  a  casserole  or  dish,  and  cover  with  hot 
water.  If  not  loose,  fill  the  crucible  with  hot  water  and 
digest  until  the  mass  breaks  up  ;  then  remove  to  the  dish. 
Cover  the  latter  with  a  watch-glass  and  add  20  cc.  of  di- 
lute hydrochloric  acid.  When  effervescence  ceases  remove 
the  watch-glass,  rinse  into  the  dish  and  evaporate  the  so- 
lution to  complete  dryness.  Place  the  dish  in  an  air-bath 
and  heat  at  110°  C.  for  one  hour.  Cool  the  casserole  some- 
what and  add  5  cc.  of  dilute  hydrochloric  acid  and  50  cc. 
of  hot  water.  Heat  until  the  solution  boils,  filter  and 
wash.  Heat  the  filtrate  to  boiling  and  add,  drop  by  drop, 
with  stirring  10  cc.  of  a  10  per  cent  solution  of  barium 
chlorid,  also  brought  to  boiling.  Continue  the  boiling 
and  stirring  for  a  few  minutes,  remove  the  beaker  to  a 
warm  place  and  allow  to  stand  over  night.  Decant  the 
clear  solution,  without  disturbing  the  precipitate,  through 


DETERMINA  TION  OF  SULFUR  1C  ACID        6r 

a  9  cm.  filter-paper,  wash  the  precipitate  once  or  twice 
with  hot  water  by  decantation,  then  transfer  it  to  the 
filter-paper  and  wash  well  with  hot  water.  Dry,  ignite, 
and  weigh  as  barium  sulfate,  BaSO4.  Multiply  this  weight 
by  0.34291  for  SO3. 

Notes 

When  rapid  sulfuric  acid  determinations  are  desired  the 
precipitate  of  barium  sulfate  may  be  filtered  off  in  one  hour 
after  precipitation,  or  as  soon  as  it  has  settled.  Newberry 
states  that  the  error  will  not  exceed  3  per  cent  of  the  total 
sulfuric  acid  present,  by  this  shortening  of  the  time  al- 
lowed for  precipitation. 

Some  chemists  prefer  to  work  with  a  larger  sample  than 
i  gram  when  determining  sulfuric  acid  by  solution.  In- 
deed when  the  cement  is  very  low  this  may  be  necessary. 
From  3  to  5  grams  can  be  taken  for  a  sample,  provided  the 
quantity  of  acid  used  to  decompose  the  cement  and  that  of 
barium  chlorid  to  precipitate  the  sulfur,  are  increased  also. 

A  weighed  Gooch  crucible1  with  its  asbestos  felt  filter 
may  conveniently  be  substituted  for  the  filter-paper  to  col- 
lect the  barium  sulfate  precipitate. 

Determination  of  Sulfur  Present  as  Calcium 

Sulfid 

Weigh  5  grams  of  cement  into  aporcelain  dish,  and  tritu- 
rate with  water  until  it  shows  no  further  tendency  to  set. 
Then  wash  out  into  the  flask  (Fig.  7)  and  cork  tightly. 
Two-thirds  fill  the  ten-inch  test-tube  with  a  solution  of 

1  See  page  39. 


62 


ANALYTICAL  METHODS 


lead  oxid  in  caustic  potash  made  by 
adding  lead  nitrate  solution  to  po- 
tassium hydroxid  solution  (sp.  gr. 
1.27)  until  a  permanent  precipitate 
forms,  and  then  filtering  off  the  so- 
lution through  asbestos  after  allow- 
ing the  precipitate  to  settle.  Run 
into  the  flask  by  means  of  the  fun- 
nel 50  cc.  of  dilute  hydrochloric  acid 
and  apply  heat  gently.  Finally 
bring  the  acid  to  a  boil  and  discon- 
nect the  delivery  tube  from  the 
flask  at  the  rubber  joint.  Collect 
the  precipitate  on  a  small  filter, 
wash  it  once  with  water  and  then 
while  still  moist  throw  the  precipi- 
tate and  filter  back  into  the  test- 
tube,  in  which  has  been  placed  some  powdered  potas- 
sium chlorate.  Pour  upon  the  filter  and  precipitate 
10  cc.  of  concentrated  hydrochloric  acid.  Allow  to  stand 
in  a  cool  place  until  the  fumes  have  passed  off,  then 
add  25  cc.  of  hot  water,  filter  off  the  pulp,  etc.,  and 
wash  with  hot  water.  Heat  the  filtrate  to  boiling  and  add 
ammonia  until  the  solution  is  slightly  alkaline.  Then 
acidulate  with  a  few  drops  of  hydrochloric  acid,  add  10  cc. 
of  a  10  per  cent  solution  of  barium  chlorid,  also  brought 
to  a  boil,  boil  for  a  few  minutes  and  stand  in  a  cool  place 
over  night.  Filter,  wash,  ignite,  and  weigh  as  barium 


DE  TERMINA  TION  OF  SUL  FUR  63 

sulfate.     Multiply   this   weight   by   0.30895    for   calcium 
sulfid,  CaS,  or  by  0.13734  for  sulfur,  S. 

Notes 

Instead  of  alkaline  lead  nitrate  solution,  a  solution  of 
cadmium  chlorid  made  slightly  alkaline  with  ammonia 
may  be  used  to  absorb  the  evolved  hydrogen  sulfid,  in 
which  case  the  cadmium  sulfid  precipitated,  may  be  col- 
lected upon  a  previously  weighed  filter-paper,  dried, 
weighed  and  the  sulfur  calculated  from  this  weight.  For 
this  method  use  10  grams  of  cement  for  the  sample  and 
fill  the  test-tube  two-thirds  full  of  a  solution  of  cadmium 
chlorid,  made  by  dissolving  3  grams  of  cadmium  chlorid 
in  75  cc.  of  water,  adding  ammonia  until  the  precipitate 
at  first  formed  redissolves  and  then  diluting  to  500  cc. 
Proceed  as  usual.  Collect  the  precipitate  of  cadmium 
sulfid  upon  a  small  counterpoised  filter,  or  better  in  a 
Gooch  crucible  and  felt,  wash  with  water  to  which  a  little 
ammonia  has  been  added,  dry  at  100°  C.  and  weigh  as 
cadmium  sulfid,  CdS.  The  weight  of  cadmium  sulfid  mul- 
tiplied by  0.5000  gives  the  equivalent  amount  of  calcium 
sulfid.  Calculate  the  percentage  and  report  as  such.  Calcu- 
late the  total  sulfur,  as  found  by  either  of  the  methods  on 
pages  59-60  to  calcium  sulfate,  by  multiplying  the  weight 
of  the  barium  sulfate  by  0.58565.  Now  multiply  the  per- 
centage of  calcium  sulfate  so  found  by  0.41185  and  deduct 
the  product  from  the  percentage  of  lime  (as  found  by  pre- 
cipitation as  oxalate  in  the  general  scheme).  The  differ- 
ence should  be  reported  as  calcium  oxid  or  lime,  CaO. 


64  ANALYTICAL  METHODS 

Multiply  the  percentage  of  calcium  sulfid  by  1.8872  for  its 
equivalent  in  calcium  sulfate  and  deduct  from  the  percent- 
age of  total  sulfur  calculated  as  calcium  sulfate.  Report 
the  difference  as  calcium  sulfate. 

Determination  of  Carbon  Dioxid  and  Combined 
Water 

Cements  contain  carbon  dioxid,  the  amount  varying 
from  a  mere  trace  in  a  fresh  well  burned  Portland  cement 
to  a  large  percentage  in  natural  cements.  Combined  water 
is  also  present  in  cements ;  the  amount  is,  however,  usu- 
ally very  small. 

For  carrying  out  the  determination  of  carbon  dioxid  and 
combined  water  at  the  same  time,  the  apparatus  designed 

A     aratus      by  Dr'  Porter  W'  Snimer'   of  Lafayette  Col- 
lege, Easton,  Pa.,  for  carbon  combustions,1  is 
best  suited. 

The  apparatus  as  used  for  carbon  dioxid  and  combined 
water  determinations  is  illustrated  in  Fig.  8.  It  consists 
of  the  following  parts  : 

1.  Two  aspirator  bottles,  a'  and  a",  the  upper,  a',  filled 
with  distilled  water  and  the  tube  leading  to  the  lower  bot- 
tle extending  to  the  bottom  of  the  latter. 

2.  A  potash  bulb,  b,  containing  a  solution  of  caustic  pot- 
ash of  1.27  sp.  gr.     The  form  of  bulb  shown  in  the  cut  is 
Liebig's.     Mohr's  or  any  other  form  will  do  as  well,  but 
the  Liebig  bulb  is  the  cheapest  and  answers  as  well  here 
as  the  more  expensive  forms. 

1  J.  Am.  Chem.  Soc.,  ai,  557. 


DETERMINATION  OF  CARBON  DIOXID       65 


Fig.  8. 

3.  AU  tube,  c,  filled  with  dried  granular  calcium  chlorid. 
A  straight  calcium  chlorid  tube  may  be  used  in  place  of 
the  U  tube.     It  takes  up  more  room,  however. 

4.  A  platinum  crucible,  d,  provided  with  a  water-cooled 
stopper  and  reservoir,  <?,  for  supplying  water  to  this  latter, 
and  a  round  water  trough  resting  upon   asbestos  board 
upon  a  tripod.     Fig.  9  shows  the  crucible  stopper,  etc.,  in 
detail.  The  dimensions  of  the  crucible  should  be  IT%  inches 
in  diameter  and  iT95  inches  high.     The  top  of  the  crucible 
is  stiffened  by  a  brazed  ring  of  ordinary  sheet  copper  T\ 
inch  wide,  and  fitting  closely  around  the  extreme  top  of 
the  crucible.     The  ring  should  be  made  of  sheet  metal,  so 
as   to  give  the  crucible  the   necessary  support  against 


66  ANALYTICAL  METHODS 

stretching  without  making  it  too  rigid.  The  water-cooled 
stopper  is  made  of  sheet  copper,  the  joints  being  brazed. 
The  stopper  should  be  made  as  nearly  perfectly  circular 
as  is  possible,  and  free  from  indentations  or  imperfections 
in  the  brazing.  The  sides  of  the  stopper  should  not  flare 
more  than  the  sides  of  the  crucible  at  the  top.  Too  much 
flare  has  the  tendency  to  cause  the  stopper  to  be  forced  out 
when  under  pressure.  The  stopper  is  somewhat  smaller 
in  diameter  than  the  crucible  opening,  in  order  to  allow 
space  for  a  rubber  band.  This  band  may  be  obtained  of 
stationers,  and  is  of  black  rubber  X  to  l/2  inch  wide,  and 
of  sufficient  length  to  stretch  tightly  around  the  lower 
part  of  the  stopper.  The  crucible  rests  with  its  bottom 
through  a  circular  opening  in  a  piece  of  T35  inch  asbestos 
board  which  in  turn  rests  upon  a  tripod.  Fig.  9  shows 
the  position  of  the  circular  water  trough,  and  Fig.  8  that 
of  the  reservoir  for  supplying  water  to  the  stopper. 

5.  A  small  U  tube,/,  filled  with  dried  granular  calcium 
chlorid.     The  best  form  is  that  shown,  provided  with  side 
arms  and  glass  stop-cocks. 

6.  A  potash  bulb,  g,  with  calcium  chlorid  tube  attached. 
The  bulb  should  be  filled  with  caustic  potash  of  1.27  specific 
gravity,  and  the  tube  with  dried  granular  calcium  chlorid. 

7.  A  guard  tube,  /t,  filled  with  dried  granular  calcium 
chlorid. 

Fill  the  reservoir,  e,  with  boiling  water.  Half  fill  the 
crucible  with  freshly  ignited  asbestos,  and  close  it  with 
the  water-cooled  stopper.  In  putting  in  this  latter  do  not 


DE  TERM  IN  A  TION  OF  CARBON  DIOXID       67 


Ait-  inlet-. 


brace  the  thumb  against  the  overflow  tube,  as  this  would 
risk  bending  the  stopper  at  the  base  of  the  overflow.     See 
.  that  the  apparatus  is  perfectly  tight  by  run- 

A  anftus6  *""&  tne  aspirator  and  pinching  the  tube  to- 
gether just  after  the  potash  bulb.  Saturate  a 
Ion?  piece  of  wick  with 
alcohol  and  wrap  it  twice 
around  the  crucible  as 
the  latter  rests  in  its 
place  upon  the  asbestos 
board  and  allow  the  ends 
of  the  wick  to  lie  in  the 
trough  as  shown  in  Fig. 
9.  Open  the  clamp  and 
allow  water  to  run  out 
of  the  stopper.  Place  a 
Bunsen  burner  under 
the  crucible.  Open  the 
clamp  between  the  lower 
aspirator  bottle  and  the 
pctash  bulb,  b,  and  reg- 
ulate the  current  of  air 
through  the  apparatus 
slcwly  for  about  twenty 
minutes.  Detach  the 
potash  bulb,  g,  and  the 
calcium  chlorid  tube,  /, 


Fig.  9. 


and  weigh.     Again  connect  the  bulb  and  tube  in  the  train 


68  ANALYTICAL  METHODS 

and  aspirate  air  slowly  through  the  apparatus  for  another 
twenty  minutes.  Detach  the  bulb,  g,  and  tube,  /,  and 
again  weigh  them.  This  weight  should  agree  to  within 
0.0005  of  the  former  weight  for  the  potash  bulb,  and  0.0003 
for  the  calcium  chlorid  tube.  If  not,  after  making  sure 
there  is  no  leakage  in  the  apparatus,  repeat  the  test.  When 
the  weights  agree  within  the  limits  given,  take  the  last 
pair  as  the  weights  of  the  bulb  and  tube,  and  proceed  with 
the  determination. 

Weigh  into  the  crucible  from   2  to  5  grams  of  cement, 

cover  with  ignited  asbestos  and  stopper  tightly.     Test  the 

apparatus   and   be   sure   there  is  no  leakage. 

Place  the  Bunsen  burner  under  the  crucible 
initiation. 

after  starting  the  hot  water  to  flowing  through 

the  stopper  and  wrapping  the  wick  around  the  crucible 
twice.  Cause  a  slow  current  of  air  from  the  aspirator  bot- 
tles to  flow  through  the  apparatus.  After  ten  minutes  re- 
place the  Bunsen  burner  by  a  blast-lamp  and  continue  the 
ignition  for  twenty  minutes.  Remove  the  lamp  and  aspi- 
rate air  through  the  apparatus  for  ten  minutes  longer. 
Detach  the  potash  bulb,  g,  and  the  calcium  chlorid  tube, 
/,  and  weigh.  The  increase  in  weight  of  the  former  repre- 
sents the  carbon  dioxid,  CO2,  and  of  the  latter  water,  H2O. 

Notes 

In  this  method  the  combined  water  and  the  carbon  di- 
oxid are  driven  out  of  the  cement  by  ignition  ;  the  former 
is  absorbed  in  a  weighed  calcium  chlorid  tube  and  the  lat- 


DE  TERM  IN  A  TION  OF  CARBON  DIOXID       69 

ter  in  a  weighed  potash  bulb.  The  increase  in  weight  of 
the  tube  and  bulb  respectively  represent  the  weight  of 
combined  water  and  carbon  dioxid  in  the  cement  sample. 
The  air  entering  the  apparatus  for  the  purpose  of  aspira- 
tion is  purified  of  any  water  and  carbon  dioxid  it  is  sure 
to  contain  by  passing  through  caustic  potash  and  then 
over  calcium  chlorid. 

To  make  the  upper  aspirator  bottle,  bore  a  hole  near  the 
bottom  of  a  five  pint  bottle  with  a  file  dipped  in  turpen- 
tine, and  then  slip  into  this  hole  a  bit  of  glass  tube  cov- 
ered with  an'inch  or  so  of  soft,  thick-walled  rubber  tubing. 

To  fill  the  potash  bulbs  attach  a  short  piece  of  rubber 
tubing  to  one  end  and  dipping  the  other  end  in  the  caustic 
potash  solution  contained  in  a  shallow  dish  apply  suction 
to  the  rubber  tubing  with  the  mouth.  When  the  bulbs 
are  filled  to  the  proper  height  (see  Fig.  14)  wipe  the  end 
dry  inside  and  outside  with  pieces  of  filter-paper. 

Instead  of  the  bulb,  b,  the  air  may  be  purified  of  any  car- 
bon dioxid  it  contains  by  causing  it  to  bubble  through 
caustic  potash  solution  contained  in  two  4  ounce  wide- 
mouthed  bottles. 

Calcium  chlorid  sometimes,  though  not  often,  contains 
calcium  oxid,  which  would  absorb  carbon  dioxid.  To 
saturate  this,  connect  the  apparatus,  leaving  out  the  pot- 
ash bulb,  /,  and  place  a  small  piece  of  marble  in  the  crucible. 
Now  heat  the  crucible  with  a  blast-lamp  and  aspirate  air 
slowly  through  the  apparatus.  Then  take  the  marble  out  of 
the  crucible  and  aspirate  air  for  twenty  minutes  longer. 


70  ANALYTICAL  METHODS 

The  potash  bulbs  and  U  tube  should  be  weighed  as  fol- 
lows :  Place  the  bulb  upon  one  balance  pan,  and  on  the 
other  the  approximate  weight.  Stand  the  U  tube  in  the 
balance  case.  Close  the  door  and  do  not  open  it  for  ex- 
actly twelve  minutes.  Then  finish  weighing  the  bulb  so 
that  the  exact  result  is  obtained  in  fifteen  minutes  from 
the  time  the  bulb  was  placed  on  the  pan.  Now  remove 
the  bulb  and  weigh  the  U  tube  quickly. 

When  not  attached  in  the  train  the  U  tube  should  have 
its  stop-cocks  turned  so  as  to  close  the  openings,  and  the 
potash  bulb  should  be  "capped  "  with  short  pieces  of  rub- 
ber tubing  containing,  in  one  end,  bits  of  capillary  glass 
tubing. 

It  is  preferable  to  weigh  the  sample  into  a  small  basket 
folded  from  platinum  foil  and  place  this  in  the  igni- 
tion crucible  rather  than  weigh  the  cement  into  the  cruci- 
ble directly. 

If  the  cement  should  contain  any  appreciable  quantity 
of  carbonaceous  matter,  such  as  unburned  coke,  this  would 
be  burned  to  carbon  dioxid  causing  high  results.  In  this 
case  first  determine  the  carbon  dioxid  given  off  on  igni- 
tion. Then  weigh  another  sample  into  the  crucible,  add 
a  little  hydrochloric  acid,  evaporate  to  dryness  and  dry  at 
100°  C.,  and  determine  the  carbon  dioxid  in  the  residue  as 
before.  This  will  represent  the  carbon  dioxid  due  to  the 
burning  of  the  organic  matter.  The  difference,  of  course, 
represents  the  carbon  dioxid  present  in  the  cement  as  car- 
bonate. 


DETERMINATION  OF  CARBON  DIOXID       71 


A  U  tube,  containing  soda-lime,  may  replace  the  potash 
bulb,  g.  This  tube  should  be  similar  iof,  and  provided  with 


Fig.  10. 

ground-glass  stoppers.     About  an  inch  of  calcium  chlorid 
should  top  the  soda-lime  in  the  limb  next  the  guard  tube,  h. 


72  ANALYTICAL  METHODS 

When  many  carbon  dioxid  determinations  have  to  be 
made,  it  will  be  found  convenient  to  arrange  the  apparatus 
on  a  stand  as  shown  in  Figs.  10  and  u.  Fig.  10  shows 


the  front  of  the  apparatus  and  Fig.  1 1  the  reverse.     The 
stand  consists  of  awooden  base  i-i  yz  inches  thick,  and  upon 


DE  TERMINA  TfON  OF  CARBON  DIOXID       73 


this  is  mounted  an  upright  board.  At  the  end  of  this 
board  and  running  entirely  across  the  base  is  fastened 
another  upright  at  right  angles  to  the  first.  These  up- 
rights support  a  shelf  upon  which  rests  the  upper  aspirator 
bottle  and  the  reservoir  for  the  water-cooled  stopper.  The 
upright  nearest  the  tripod  should  be  protected  against  the 
heat  of  the  blast-lamp  by  covering  with  a  sheet  of  asbestos. 
f^  ==^[  The  U  tubes,  etc.,  rest  upon 

shelves  as  shown.  The  manner 
I  of  clamping  the  U  tubes  to  the 
1  board  is  also  shown  in  Fig.  12. 
a'  and  a"  (Fig.  1 1)  are  aspirator 
bottles ;  b  is  filled  with  soda-lime 
and  c  with  calcium  chlorid ;  d  is 
Shimer's  special  form  of  water-jack- 
eted platinum  crucible;  e  (Fig.  10) 
is  filled  with  calcium  chlorid,  / 
with  soda-lime  topped  with  calcium 
chlorid,  and^  with  calcium  chlorid. 
Fig.  13  shows  Shimer's  special 
form  of  "water- jacketed  crucible." 
It  is  more  compact  than  the  form 
shown  in  Fig.  9  and  more  easily 
handled,  but  is  also  more  expen- 

sive'  PIUS. 

Determination  of  Carbon  Dioxid  Alone 
The  apparatus  just  described  for  carbon  dioxid  and  com- 
bined water  determinations  may,   of  course,  be  used  for 


74  ANALYTICAL  METHODS 

determining  carbon  dioxid  only.  In  this  case  it  is  not 
necessary  to  weigh  the  calcium  chlorid  tube,  f,  and  in  place 
of  the  expensive  U  tube  with  its  ground-glass  stop-cocks, 
a  simple  straight  form  calcium  chlorid  tube  can  be  used 
just  as  well.  Neither  is  it  necessary  to  supply  the  stop- 
per with  hot  water,  and  an  empty  potash  bulb  can  replace 
the  calcium  chlorid  tube,  c.  The  determination  is  carried 
out  precisely  as  if  both  the  water  and  carbon  dioxid  were 
being  considered,  with,  of  course,  the  exception  of  not 
weighing  the  tube,  /,  at  the  end  of  the  operation.  If  the 
stopper  is  wet  with  the  finger  before  insertion  into  the 
crucible,  it  will  be  found  to  go  in  easier.  This  is,  of 
course,  not  permissible  when  the  water  also  is  determined. 

Some  chemists  prefer  to  determine  carbon  dioxid  by 
liberating  this  constituent  with  hydrochloric  acid  and  ab- 
sorbing the  evolved  gas  in  a  weighed  potash  bulb. 

For  carrying  out  the  determination,  refer  to  the  appara- 
tus (Fig.  8)  for  determining  carbon  dioxid  and  combined 
water.  Omit-the  U  tube,  c,  and  substitute  for  the  crucible, 
d,  a  100  cc.  wide-mouthed  flask  provided  with  a  funnel  tube. 
Follow  the  flask  with  a  U  tube  containing  sulfuric  acid 
(sp.  gr.  1.84)  and  this  by  the  U  tube,/  the  potash  bulb,  g, 
and  the  guard  tube,  h. 

A  convenient  way  of  arranging  the  apparatus  is  shown 
in  Fig.  14.  a  is  filled  with  soda-lime  ;  b  is  a  funnel  tube 
with  ground-glass  stop-cock,  c  the  100  cc.  flask,  d  contains 
sulfuric  acid,  e  and  g  calcium  chlorid,  /  is  the  weighed 
potash  bulb,  and  h  the  aspirator  bottle. 


DETERMINATION  OF  CARBON  D I  OX  ID 


75 


Fig.  14. 

Weigh  into  the  flask,  c,  from  2  to  TO  grams  of  cement, 
triturate  with  water  until  all  tendency  to  set  has  ceased, 
and  connect  the  soda-lime  tube  a  with  the 
funnel  tube.  Aspirate  a  few  liters  of  air 
through  the  apparatus,  disconnect  and  weigh 
the  potash  bulb  with  its  attached  calcium  chlorid  tube. 
Again  connect  the  apparatus,  aspirate  another  two  liters, 
and  again  weigh  the  potash  bulb  and  attached  calcium 
chlorid  tube.  If  the  first  and  second  weights  agree  to 


The  Deter- 
mination. 


ANALYTICAL  METHODS 


within  0.0005  gram  of  each  other,  run  into  the  flask  50 
cc.  of  dilute  hydrochloric  acid  and,  if  sulfids  are  present, 
a  very  little  chromic  acid.  After  connecting  the  bulb  and 
tube  in  the  train,  and  when  action  ceases  apply  heat 
gradually  until  the  contents  of  the  flask  boil.  Connect 
the  soda-lime  tube  a  and  aspirate  air 
slowly  through  the  apparatus.  Turn 
out  the  burner  and  aspirate  two  liters 
more  of  air.  Disconnect  the  potash 
bulb  and  calcium  chlorid  tube  and 
wreigh.  The  gain  in  weight  is  car- 
bon dioxid.  Divide  the  increase  by 
the  weight  of  the  sample  used  and 
multiply  he  quotient  by  100,  for 
the  percentage  of  carbon  dioxid  in 
the  cement. 

Rapid  Determination 
When  rapid  determinations  of 
carbon  dioxid  have  to  be  made,  the 
following  apparatus, 
which  is  a  modifica- 
tion of  Rose's  form, 
may  be  used  to  advantage.  It  con- 
sists (Fig.  15)  of  a  small  50  cc.  Er- 
lenmeyer  flask,  a,  provided  with  a 
two-hole  rubber  stopper.  Through  one  hole  of  this  lat- 
ter passes  a  3  inch  calcium  chlorid  tube,  b,  and  through  the 
other  a  piece  of  bent  glass  tubing,  c,  one  arm  of  which 


The  Appa- 
ratus. 


DETERMINATION  OF  CARBON  DIOXID       77 

reaches  nearly  to  the  bottom  of  the  flask,  the  other  through 
another  stopper  to  the  bottom  of  a  small  wide  tube,  d. 
This  latter  is  made  from  a  5  inch  test-tube.  Such  an  ap- 
paratus will  weigh  from  35  to  60  grams  according  to  the 
skill  and  choice  of  materials  with  which  it  is  made. 

Place  a  little  wool  or  cotton  in  the  bottom  of  the  calcium 

chlorid  tube  and  then  fill  the  tube  with  calcium  chlorid. 

Next  two-thirds  fill  the  tube,  d,  with  dilute 

hydrochloric  acid,   and   weigh  into  the  flask 
mmation. 

from   2  to  3  grams  of  Portland  cement,  or  i 

to  2  grams  of  natural  cement.  Moisten  the  cement  thor- 
oughly with  water,  place  the  stopper  in  the  flask,  cap  the 
openings,  o'  and  o",  with  pieces  of  rubber  tubing  closed 
at  one  end  with  bits  of  glass  rod,  and  set  in  the  balance 
case.  After  ten  minutes  weigh.  Now  attach  a  small 
guard  tube,  filled  with  calcium  chlorid,  to  the  opening,  o', 
and  after  uncapping,  o",  suck  the  acid  from  the  tube,  d, 
into  the  flask,  a.  As  soon  as  the  acid  is  all  in  a,  close 
o"  with  the  finger  and  cap  quickly.  Remove  the  guard 
tube,  and  after  effervescence  ceases  place  the  apparatus  on 
a  hot  plate  until  the  contents  of  the  flask  begin  to  boil. 
Remove  from  the  hot  plate,  cap  the  opening,  o' ',  and  set 
aside  until  the  apparatus  cools  to  the  temperature  of  the 
room.  Uncap  0",  attach  the  guard  tube  to  this  opening 
this  time,  uncap  o'  and  blow  air  gently  through  the  appa- 
ratus for  five  to  seven  minutes.  Cap  the  openings,  place 
in  the  balance  case  and  after  ten  minutes  weigh.  Always, 
before  weighing,  uncap  either  of  or  o"  for  a  few  seconds 
and  then  recap.  This  allows  the  pressure,  caused  by 


78  ANALYTICAL  METHODS 

change  of  temperature,  to  adjust  itself.  The  loss  in  weight 
represents  the  carbon  dioxid,  CO2,  in  the  cement.  Divide 
the  loss  by  the  weight  of  the  sample  and  multiply  the 
result  by  too  for  the  percentage. 

Loss  on  Ignition 

Weigh  2  grams  of  cement  into  a  weighed  platinum  cruci- 
ble, cover  with  a  lid,  and  heat  for  five  minutes  over  a  Bun- 
sen  burner,  starting  with  a  low  flame  and  gradually  rais- 
ing it  to  its  full  height.  Then  heat  for  fifteen  minutes 
over  a  blast-lamp.  Cool  and  weigh.  The  loss  of  weight 
represents  the  loss  on  ignition.  This  loss  consists  mainly 
of  combined  water  and  carbon  dioxid  driven  off  by  the 
high  temperature.  Some  chemists  report,  therefore,  as 
' '  carbon  dioxid  and  water, ' '  or  having  found  the  carbon 
dioxid,  subtract  the  percentage  from  that  of  the  ' '  loss  on 
ignition  "  and  call  the  remainder  "  water  of  combination  " 
or  combined  water. 

Determination  of  Alkalies 

(J.  Lawrence  Smith's  Method) 

Mix  i  gram  of  the  finely  ground  cement  with  i  gram  of 
ammonium  chlorid  by  grinding  together  in  a  clean  agate 
mortar  placed  upon  a  sheet  of  black  glazed  paper.  Add  8 
grams  of  calcium  carbonate  free  from  alkalies,  and  trans- 
fer the  mixture  to  a  large  platinum  crucible  provided  with 
a  closely-fitting  cover.  Heat,  gently  at  first,  over  a  Bun- 
sen  burner,  then  gradually  raise  the  temperature  to  a  full 
red  heat  and  keep  so  for  an  hour.  Cool  the  crucible,  and 


DE  TERM  IN  A  TION  OF  AL  K A  LIES  79 

if  loose,  transfer  the  sintered  mass  to  a  small  beaker,  or 
better  a  platinum  dish.  Wash  the  crucible  and  lid  with 
hot  water  and  pour  into  the  dish  or  beaker.  Digest  the 
contents  of  the  beaker  until  the  sintered  mass  slakes  to  a 
fine  powder. 

If  the  sintered  mass  is  not  easily  detached  from  the  cruci- 
ble, put  the  crucible  into  the  beaker,  add  hot  water  and 
digest  with  heat  until  the  mass  slakes.  Remove  the  cru- 
cible and  wash  it  off  into  the  beaker.  Now  filter  into  an- 
other platinum  dish  or  beaker  and  wash  the  residue  with 
water.  Add  1.5  grams  of  pure  ammonitim  carbonate,  evap- 
orate carefully  to  about  50  cc.  and  add  a  little  more  am- 
monium carbonate  and  a  few  drops  of  ammonia.  Filter 
on  a  small  filter  into  a  dish  of  platinum  or  porcelain.  Test 
the  filtrate  with  a  few  drops  of  ammonium  carbonate  solu- 
tion to  make  sure  all  the  calcium  has  been  precipitated. 
Evaporate  to  dryness  and  ignite  at  ^a  barely  visible  red 
until  all  the  ammonia  salts  are  expelled  and  white  fumes 
cease  to  come  off.  Cool,  dissolve  in  a  little  water,  add  a 
few  drops  of  ammonium  carbonate  solution  and  of  ammo- 
nia, and  filter  from  any  residue  that  may  form.  Add 
three  or  four  drops  of  dilute  hydrochloric  acid  to  the  fil- 
trate and  evaporate  to  dryness  in  a  weighed  platinum  dish. 
Ignite  carefully  as  before  and  weigh  as  sodium  chlorid  and 
potassium  chlorid,  Nad  +  KC1.  Dissolve  the  mixed 
chlorids  in  water  (they  should  be  soluble  without  residue), 
and  add  to  the  solution  an  excess  of  platinic  chlorid  solu- 
tion. Evaporate  nearly  to  dryness  on  the  water-bath, 
add  20  cc.  of  So  per  cent  alcohol  and  let  stand  until  the 


8o  ANALYTICAL  METHODS 

sodium  salts  dissolve.  Filter  on  a  weighed  Gooch  cruci- 
ble or  a  counterpoised  filter,  wash  with  80  per  cent  alcohol 
until  the  washings  run  through  perfectly  colorless,  dry 
and  weigh  as  potassium  platinic  chlorid,  K2PtCl6.  Mul- 
tiply the  weight  by  0.19398  for  potassium  oxid,  K2O.  To 
calculate  the  sodium  oxid,  multiply  the  weight  of  the  po- 
tassium plantinic  chlorid  by  0.30701  and  subtract  this 
from  the  weight  of  the  residue  of  potassium  and  sodium 
chlorid;  the  difference  multiplied  by  0.53076  gives  the 
weight  of  i  gram  of  sodium  oxid,  Na.,O. 

Notes 

Stillman1  gives  a  scheme  for  the  analysis  of  cement  in 
which  the  alkalies  and  sulfuric  acid  are  determined  in  the 

same  sample  with  the  silica,  iron  and  alu- 
Alkahes,  .  , 

„....  mma,  lime  and  magnesia.     The  outline  01  his 

scheme  is  given  below,  though  the  author  does 
not  recommend  it,  and  believes  it  offers  many  chances  for 
errors  in  the  determination  of  the  alkalies. 

Weigh  2  grams  of  finely-ground  dried  cement  into 
a  6  inch  dish,  add  50  cc.  of  dilute  hydrochloric  acid 
and  5  cc,  of  nitric  acid,  and  evaporate  to  dryness.  Re- 
dissolve  in  25  cc.  hydrochloric  acid  and  100  cc.  water, 
boil  and  filter  into  a  250  cc.  graduated  flask.  Wash  the 
residue  well,  allowing  the  washing  to  run  into  the  flask  and 
make  the  solution  up  to  the  mark.  Determine  the  silica 
in  the  residue,  and  also  the  alumina  as  directed  on  page  26. 
From  the  flask,  measure  out  a  portion  of  exactly  50  cc.  and 

1  Stilltnan's  "Engineering  Chemistry,"  p.  260. 


DETERMINA  TION  OF  ALKALIES  81 

determine  the  sulfur  trioxid  as  directed  on  page  59,  by 
boiling  and  adding  barium  chlorid.  Measure  another  por- 
tion of  exactly  100  cc.  into  a  300  cc.  beaker  and  precipitate 
the  iron  and  alumina  with  ammonia  and  the  lime  with  am- 
monium oxalate  as  usual.  Evaporate  the  nitrate  from  the 
lime  to  dryness  in  a  platinum  dish.  Ignite  at  a  low  red 
heat  to  expel  ammonium  salts,  add  50  cc.  of  water,  boil, 
filter,  and  wash.  Dry,  ignite  and  weigh  the  residue  as 
magnesium  oxid,  MgO.  Transfer  the  filtrate  from  the 
magnesia  to  a  weighed  platinum  dish,  add  a  few  drops  of 
sulfuric  acid  and  evaporate  to  dryness.  Ignite  at  a  low 
red  heat  to  a  constant  weight.  This  weight  represents 
Na,SO4  +  K2SO4  +  trace  MgSO4.  Dissolve  in  50  cc.  of 
water,  mix  well  and  divide  into  two  portions  of  25  cc. 
each.  To  the  first  portion  add  a  few  drops  of  hydrochloric 
acid,  then  make  alkaline  with  ammonia  and  precipitate 
the  magnesium  with  sodium  hydrogen  phosphate.  Set 
the  solution  aside  three  hours,  filter,  wash,  dry,  ignite, 
and  weigh  as  magnesium  pyrophosphate,  Mg2PsO?.  Calcu- 
late to  MgSO4  by  multiplying  this  weight  by  1.0808.  The 
result  multipled  by  2  is  to  be  subtracted  from  the  weight 
of  Na2SO4  +  K2SO4  +  trace  MgSO4.  The  resultis  Na2SO4 
+  K2SO4.  Calculate  the  Mg,P,O7  after  multiplying  by  2 
also  to  MgO,  and  add  to  that  found  above.  To  the  second 
portion  add  a  solution  of  platinic  chlorid  in  slight  excess 
and  a  few  drops  of  hydrochloric  acid.  Evaporate  to  dry- 
ness  on  a  water-bath,  redissolve  the  sodium  salt  in  a  little 
80  per  cent  alcohol  and  warm,  and  filter  on  a  weighed 
Gooch  crucible.  Weigh  and  calculate  the  K2PtCl6  to 


82  ANALYTICAL  METHODS 

K2SO4  by  multiplying  by  0.35884.  Multiply  the  result  by 
2  and  subtract  the  weight  of  the  Na2SO4  +  K,SO4.  The 
remainder  represents  the  Na2SO4.  Calculate  the  K2SO4  to 
K2O  by  multiplying  by  0.54057,  and  the  Na2SO4  to  NaaO 
by  multiplying  by  0.43680.  It  must  be  borne  in  mind  the 
fraction  of  the  sample  each  precipitate  represents  in  this 
scheme  as  the  weight  of  silica  should  be  multiplied  by  100 
and  divided  by  the  weight  of  the  sample,  while  the  lime 
should  be  multipled  by  100  and  divided  by  f  the  weight 
of  the  sample  for  the  per  cent. 

THE  ANALYSIS  OF  CEMENT  MIXTURES, 
SLURRY,  ETC. 

Since  the  success' of  cement-making  depends  primarily 
upon  the  proper  portion  of  carbonate  of  lime  to  silica  and 
alumina  in  the  cement  mixture,  it  is  highly  important  to 
be  able  to  rapidly  estimate  this  ratio.  If  the  materials 
from  which  the  mixture  is  made  are  of  normal  constitu- 
tion a  determination  in  it  of  the  calcium  carbonate  alone 
will  suffice  to  check  the  correctness  of  the  mixture. 

For  rapidly  checking  the  percentage  of  calcium  carbo- 
nate, two  methods  are  in  general  use,  the  alkalimetric 
method  in  which  the  calcium  carbonate  is  decomposed  by 
a  measured  quantity  of  standard  nitric  or  hydrochloric 
acid  and  the  excess  of  acid  determined  by  titration  with 
standard  alkali,  and  the  indirect  gas  method  in  which  the 
carbonate  of  lime  is  decomposed  by  acid  and  the  evolved 
carbon  dioxid  gas  collected  in  a  suitable  apparatus  and 


CALCIUM  CARBONATE  IN  CEMENT          83 

measured  ;  since  the  CO2  is  proportional  to  the  CaCO3, 
the  percentage  of  lime  can  be  calculated  from  the  volume 
of  CO2.  For  the  latter  method  the  Scheibler's  calcimeter  is 
used.  Neither  of  these  methods  gives  very  accurate  results, 
and  when  the  exact  composition  of  the  mixture  is  desired 
resort  must  be  had  to  one  of  the  longer  gravimetic  methods 
given  further  on. 

When  the  slurry  of  the  wet  process  is  analyzed  it  should 
first  be  evaporated  to  dryness  in  a  porcelain  dish,  then 
finely  pulverized  in  a  mortar  and  again  dried  for  half  an 
hour  at  no°C.  It  will  then  be  free  from  moisture  and 
ready  for  analysis. 

Rapid   Methods  for  Checking  the  Percentage  of 
Calcium  Carbonate  in  Cement  Mixtures 

By  Standard  Acid  and  Alkali 

Dissolve  i  gram  of  phenolphthalein  in  100  cc.  of  alcohol 
(50  per  cent) .     Keep  in  a  small  bottle  provided  with  a  per- 
forated stopper  through  which  passes  a  small 
Phenol-  .  ir  f 

nhthalein        pipette,  made  from  a  piece  of  5  inch  narrow 
bore  glass  tubing  by  drawing  out  one  end  to 
a  fine  opening.     One  drop  of  this  solution  is  sufficient  for 
a  determination. 

Weigh  rapidly  and  roughly  20  grams  of  clean,  bright, 
freshly  cut  metallic  sodium.  Cut  in  small  pieces  about 

the  size  of  a  pea,  and  keep  in  a  small  beaker 
Standard  Z 

N  Sodium°  petroleum.     Dry  a  piece  of  sodium  between 

Hydroxid.       filter-papers  and  drop  into  a  porcelain  or  sil- 
ver dish  containing  from  250  to  500  cc.  of 


84  ANALYTICAL  METHODS 

freshly  boiled,  cold  distilled  water.  When  action  ceases 
dry  another  piece  of  sodium  and  drop  into  the  dish  and  re- 
peat until  all  the  sodium  is  dissolved.  During  the  solu- 
tion of  the  metal  keep  the  dish  covered  with  a  watch-glass 
or  an  inverted  funnel  whose  diameter  is  slightly  smaller 
than  that  of  the  dish.  When  all  the  sodium  has  been  dis- 
solved, rinse  off  the  funnel  or  watch-glass  into  the  dish. 
Make  up  the  solution  to  2  liters,  and  keep  in  a  tightly 
stoppered  bottle. 

Take  the  specific  gravity  of  the  dilute  nitric  acid  (i  :  i) 
used  in  the  laboratory,  by  means  of  a  hydrometer.     Refer 

to  the  table  in  the  appendix  showing  the 
Standard  i 

N  Nitric  °  strength  of  nitric  acid  of  different  densities 
Add  arjd  calculate  from  the  seventh  column  what 

quantity  of  the  dilute  acid  contains  50  grams 
of  HNO3.  Measure  out  this  volume  carefully  into  a  2  liter 
graduated  flask  and  dilute  to  the  mark.  Mix  and  pre- 
serve in  a  glass-stoppered  flask  or  bottle. 

Measure  with  a  pipette  50  cc.  of  the  f  normal  acid  intoa  250 
cc.  flask  and  add  a  few  drops  of  the  phenolphthalein  indi- 
cator.    Fill  a  burette  with  the  \  normal  al- 
otandardizmg 

and  Checking  anc*  run  *nto  tne  ac^   until  a  purple- 

the  Solution.  rec^  color  is  produced.  Take  the  reading 
of  the  burette.  Repeat  this  test  until  re- 
sults agree  closely.  Grind  finely  in  an  agate  mortar  20  to  25 
grams  of  purest  Iceland  spar.  Dry  in  an  air-bath  for  one 
hour  at  110°  C.  and  keep  in  a  glass -stoppered  bottle. 
Weigh  carefully  0.5  gram  of  this  into  the  250  cc.  flask. 


CALCIUM  CARBONATE  IN  CEMENT          85 

Provide  the  latter  with  a  perforated  stopper  through  which 
passes  a  glass  tube  2  feet  long  drawn  out  to  a  small  jet  at 
the  upper  end.  Measure  into  the  flask  50  cc.  of  the  f  normal 
acid  and  stopper  tightly.  When  all  action  ceases  place 
the  flask  still  stoppered  on  the  hot  plate  and  heat  to  boil- 
ing for  a  few  minutes.  Remove  from  the  source  of  heat, 
unstopper,  reverse  the  glass  tube,  and  rinse  out  into  the 
flask.  Add  a  few  drops  of  phenolphthalein  and  titrate  with 
the  I  normal  alkali  until  a  purple-red  color  appears.  De- 
duct the  number  of  cubic  centimeters  required  from  that 
necessary  to  neutralize  50  cc.  of  the  acid  alone.  The  dif- 
ference will  be  the  number  of  cubic  centimeters  of  stand- 
ard alkali  equivalent  to  0.5  gram  CaCO3,  or  0.28  gram  of 
CaO.  0.28  divided  by  this  difference  will  give  the  weight 
of  calcium  oxid  equivalent  to  i  cc.  of  the  \  normal  alkali. 
Weigh  into  the  above-mentioned  flask  i  gram  of  the 
cement  mixture  or  dried  slurry,  add  50  cc.  of  f  normal  acid 
.  from  a  burette  or  pipette  and  stopper  the  flask 

tightly  with  its  perforated  stopper.  When 
action  ceases  place  on  the  hot  plate  and  boil 
briskly  for  a  few  minutes,  remove,  rinse  out  the  tube,  add 
phenolphthalein  to  the  contents  of  the  flask  and  run  in 
the  f  normal  alkali  until  the  solution  turns  rosy  pink.  Sub- 
tract the  number  of  cubic  centimeters  required  to  neutral- 
ize the  excess  of  acid  from  that  required  to  neutralize  50 
cc.  of  acid  alone,  multiply  the  difference  by  the  CaO  equiv- 
alent to  i  cc.  of  the  alkali,  the  result  multiplied  by  100 
will  be  the  per  cent  of  lime  (CaO)  in  the  mixture. 


86  ANALYTICAL  METHODS 

Notes 

The  process  depends  upon  the  decomposition  of  the  cal- 
cium carbonate  by  a  measured  quantity  of  standard  acid 
in  excess  of  that  required  by  theory. 

CaC03  +  2HN03  •=  Ca(N03)2  +  H2O  +  CO2. 
Since  the  molecular  weight  of  calcium  carbonate  is  100, 
and  of  nitric  acid  63,  100  grams  of  CaCO3  =126  grams 
HNO  ;  arid  as  a  liter  of  normal  nitric  acid  contains  63 
grams  of  HNO3,  50  grams  of  CaCO3  will  require  a  liter  of 
normal  acid  for  its  decomposition,  or  z\  (f)  liters,  or  2,500 
cc.  of  |  normal  acid.  Hence  0.5  gram  of  calcium  carbonate 

would  require  —  of  this  volume  or  25  cc.  of  f  normal  nitric 

acid.  The  excess  of  nitric  acid  is  then  found  by  titration 
against  \  normal  alkali,  using  phenolphthalein  or  methyl 
orange  as  an  indicator  of  the  end  of  the  reaction. 

Phenolphthalein  is  a  very  delicate  indicator.  It  is,  how- 
ever, very  susceptible  to  carbon  dioxid,  and  the  solution 
must  be  freed  from  the  latter  by  boiling  whenever  this  in- 
dicator is  used.  It  is  also  useless  in  the  presence  of  free 
ammonia  or  its  compounds.  The  addition  of  a  few  drops 
of  the  indicator  to  an  acid  or  neutral  solution  shows  no 
color,  but  the  faintest  excess  of  caustic  alkali  gives  a  sud- 
den change  to  purple  red.  Methyl  orange  may  be  used  in 
place  of  phenolphthalein.  While  not  so  delicate  it  pos- 
sesses certain  advantages  over  the  latter.  It  can  be  used 
in  the  cold  with  carbonates,  and  its  delicacy  is  not  im- 
paired by  the  presence  of  ammonia  or  its  salts.  A  con- 


CALCIUM  CARBONATE  IN  CEMENT          87 

venient  strength  for  the  methyl -orange  indicator  is  o.  i 
gram  of  the  salt  to  100  cc.  of  water.  One  drop  of  this  so- 
lution is  sufficient  for  100  cc.  of  any  colorless  solution. 
Alkaline  liquids  are  faintly  yellow  with  methyl-orange 
and  acid  ones  are  pink. 

Sodium  hydroxid  solution  can  be  prepared  from  caustic 
soda  itself  instead  of  metallic  sodium.  The  advantage 
which  the  latter  has  over  the  former  is  that  it  gives  an 
alkali  solution  free  from  carbonate,  and  hence  one  with 
which  phenolphthalein  may  be  used  as  an  indicator  with- 
out boiling.  Instead  of  the  method  from  sodium  described 
above  the  chemist  may  pursue  the  following  plan  of  making 
the  I  normal  alkali  and  use  methyl-orange  for  an  indicator. 

First  prepare  the  f  normal  nitric  acid.  Next  dissolve 
about  44  grams  of  caustic  soda  in  2\  liters  of  distilled 
water.  Determine  the  strength  of  this  solution  by  titra- 
tion  of  10  or  20  cc.  against  the  f  normal  acid,  and  dilute 
the  sodium  hydroxid  so  that  i  cc.  shall  exactly  neutral- 
ize i  cc.  of  |  normal  acid.  The  number  of  cubic  centimeters 
of  water  necessary  to  add  to  2  liters  of  the  potassium 
hydroxid  solution  in  order  to  make  it  of  such  strength, 

may  be  found  by  the  formula  f—   —  i  J    X  2,000;    when 

b  =  cc.  of  acid  required  to  neutralize  a  cc.  of  soda. 

Instead  of  f  normal  caustic  soda  the  corresponding  f  nor- 
mal caustic  potash  may  be  used.  To  prepare,  substitute 
55  grams  of  KOH  for  44  grams  of  NaOH,  and  proceed  as 
above. 


ANALYTICAL  METHODS 


Fig.  1 6  shows  a  convenient  apparatus  for  keeping  the 
caustic  soda  solution.  A  is  a  5  pint  acid  bottle  resting 
upon  a  shelf  over  a  table  in 
a  good  light.  The  rubber 
stopper  of  the  bottle  con- 
tains two  holes.  Through 
one  hole  passes  a  calcium 
chlorid  tube  B,  the  bulb  of 
which  is  filled  with  absorb- 
ent cotton.  The  tube  itself 
is  filled  with  soda-lime. 
The  object  of  this  tube  is  to 
free  any  air  that  may  enter 
the  bottle  of  its  carbon  di- 
oxid  and  thus  keep  the  so- 
lution free  of  carbonates. 
Through  the  other  perfora- 
tion in  the  stopper  passes 
the  long  glass  tube  c  bent 
in  the  form  shown,  and 
reaching  to  the  bottom  of 
the  bottle.  The  other  end 
of  the  tube  passes  inside  a 
two-hole  rubber  stopper  in 
the  mouth  of  the  burette 
and  extends  to  the  zero  mark  of  the  latter.  The  burette 
passes  through  a  hole  in  the  shelf  and  is  held  in  position  by 
a  wedge.  To  fill  the  burette,  suction  is  applied  to  the  rub- 


CALCIUM  CARBONATE  IN  CEMENT          89 

her  tube  d,  which  is  connected  with  a  short  piece  of  glass 
tubing  passing  through  the  other  perforation  in  the  burette 
stopper.  Since  alkalies  act  on  the  glass  stop-cocks  of  the 
ordinary  burette  causing  them  to  stick,  the  old-style  Mohr's 
form  with  its  rubber  connection,  glass  tip  and  pinch -cock 
is  best  for  use  with  the  alkali  solution. 

Instead  of  f  normal  caustic  alkali,  f  normal  carbonate  may 
be  used.  Ignite  pure  dry  sodium  carbonate  gently  for  fifteen 
or  twenty  minutes,  cool  in  a  desiccator  and  weigh  quickly 
exactly  42.4  grams  into  a  fairly  large  beaker.  Dissolve 
in  water  and  pour  into  a  2-liter  graduated  flask.  Rinse 
out  the  beaker  into  the  flask  and  dilute  to  the  mark.  Each 
cubic  centimeter  of  this  solution  is  equivalent  to  0.0112 
gram  of  lime,  CaO.  When  this  alkali  is  used  with  the 
acid  it  is  unnecessary  to  standardize  the  solutions  by  the 
use  of  Iceland  spar.  Methyl-orange  and  not  phenolphtha- 
lein  must  be  used  as  an  indicator  with  this  solution. 

The  following  is  an  example  of  the  preparation  of 
the  |  normal  nitric  acid ;  The  specific  gravity  of  the  nitric 
acid  was  found  by  the  hydrometer  to  be  1.19  ;  referring  to 
the  table  of  "Specific  Gravities  of  Nitric  Acid  "  in  the  in- 
dex, i  liter  of  acid  of  1.19  sp.  gr.  contains  0.367  kilogram 
or  367  grams  of  HNO3. 

To  find  the  quantity  of  acid  containing  50  grams  of 
HXO, : 

367  :  1000  ::  50  :  x 

x  =  136.2  cc.  =  volume  of  1.19  sp.  gr.  acid  containing 
50  grams  HNO3. 


9° 


ANALYTICAL  METHODS 


Hence  136.2  cc.  of  the  nitric  acid  were  measured  off  into 
a  two-liter  flask  and  diluted  to  the  mark, 

Another  way  of  preparing  the  acid  is  first  to  make  up 
the  I  normal  sodium  carbonate  solution  as  mentioned  above. 
Then  titrate  2  cc.  of  the  dilute  acid  with  the  f  normal  so- 
dium carbonate.  Next  calculate  the  quantity  of  acid  which 
would  be  required  to  neutralize  2  liters  of  the  latter,  and 
after  measuring  this  amount  into  a  flask,  dilute  to  2  liters. 
Tnis  latter  solution  must  be  rechecked  against  the  sodium 
carbonate. 

To  make  acid  and  alkali  agreeing  with  each  other  cubic 
centimeter  for  cubic  centimeter,  prepare  2\  liters  of  acid 
a  little  stronger  than  •  normal  by  either  of  the  two  methods 
just  given  (taking  specific  gravity  on  trial  against  f  nor- 
mal alkali),  and  determine  its  exact  strength  by  dupli- 
cate tests  against  f  normal  sodium  carbonate.  Dilute  this 
acid  solution  so  that  i  cc.  shall  exactly  neutralize  i  cc.  of 
the  sodium  carbonate.  The  number  of  cubic  centimeters 
of  water  it  is  necessary  to  add  to  two  liters  of  the  acid  so- 
lution may  be  found  by  the  formula  (—  —  i  J  X  2000, 

where  b  —  cc.  of  soda  required  to  neutralize  a  cc.  of  acid. 
After  dilution  check  the  strength  by  titration  against 
the  |  normal  sodium  carbonate. 

Instead  of  nitric  acid,  hydrochloric  acid  may  be  used. 
Prepare  the  f  normal  hydrochloric  acid  similar  to  the  f  nor- 
mal nitric  acid,  except  as  regards  the  quantity  of  acid.  A 
liter  of  |  normal  hydrochloric  acid  should  contain  14.6 


CALCIUM  CARBONATE  IN  CEMENT          91 

grams  hydrochloric  acid  to  the  liter.  This  solution  may 
be  standardized  gravimetrically  as  follows  : 

To  any  convenient  quantity  of  the  acid  to  be  standard- 
ized, add  solution  of  silver  nitrate  in  slight  excess,  and  2 
cc.  pure  nitric  acid  (sp.  gr.  1.2).  Heat  to  boiling-point, 
and  keep  at  this  temperature  for  some  minutes  without 
allowing  violent  ebullition,  and  with  constant  stirring, 
until  the  precipitate  assumes  the  granular  form.  Allow 
to  cool  somewhat,  and  then  filter  through  asbestos.  Wash 
the  precipitate  by  decantation,  with  200  cc.  of  very  hot 
water,  to  which  has  been  added  8  cc.  of  nitric  acid  and  2 
cc.  of  dilute  solution  of  silver  nitrate  containing  i  gram 
of  the  salt  in  100  cc.  of  water.  The  washing  by  decanta- 
tion is  performed  by  adding  the  hot  mixture  in  small 
quantities  at  a  time  beating  up  the  precipitate  well  with 
a  thin  glass  rod  after  each  addition.  The  pump  is  kept 
in  action  all  the  time ;  but  to  keep  out  dust  during  the 
washing,  the  cover  is  only  removed  from  the  crucible  when 
the  fluid  is  to  be  added. 

Put  the  vessels  containing  the  precipitate  aside,  return 
the  washings  once  through  the  asbestos  so  as  to  obtain 
them  quite  clear,  remove  from  the  receiver,  and  set  aside 
to  recover  the  silver.  Rinse  the  receiver  and  complete  the 
washing  of  the  precipitate  with  about  200  cc.  of  cold  water. 
Half  of  this  is  used  to  wash  by  decantation  and  the  re- 
mainder to  transfer  the  precipitate  to  the  crucible  with  the 
aid  of  a  trimmed  feather.  Finish  washing  in  the  crucible, 
the  lumps  of  silver  chlorid  being  broken  down  with  a  glass 


92  ANALYTICAL  METHODS  ' 

rod.  Remove  the  second  filtrate  from  the  receiver  and 
pass  about  20  cc.  of  alcohol  (98  per  cent)  through  the  pre- 
cipitate. Dry  at  from  140°  to  150°.  Exposure  for  half 
an  hour  is  found  more  than  sufficient  at  this  temperature, 
to  dry  the  precipitate  thoroughly.  The  weight  of  silver 
chlorid  multiplied  by  0.25424  gives  the  hydrochloric  acid 
in  the  volume  taken. 

It  will,  in  some  laboratories,  be  found  more  convenient 
to  make  up  \  normal  hydrochloric  acid,  standardize  by  pre- 
cipitation with  silver  nitrate,  and  keep  for  use  only  in  pre- 
paring and  standardizing  the  •§•  normal  acid  and  alkali  ac- 
tually used.  For  example:  10  cc.  of  such  a  |  normal  hy- 
drochloric acid  solution  gave,  on  checking  with  silver  ni- 
trate, 0.5751  gram  silver  chlorid. 

A  I  normal   solution   should  give  T  iJ^jL* 

or  0.5740  gram  AgCl.     Hence  the  solution  is  a  little  above 

|  normal  strength,  and  a  factor     '         or    1.002    must  be 
0.5740 

used  with  it.  Ten  cc.  of  a  solution  made  by  dissolving  16.5 
grams  of  caustic  soda  in  i  liter,  required  10.15  cc-  of 
the  above  acid  —  10.15  X  1.002  =  10.17  cc.  of -§  normal. 
This  made  the  value  of  i  cc.  of  the  alkali  =  10.17  X  0.0112 
-5-  10  =  0.01139  gram  of  CaO.  Wishing  to  prepare  alkali 
of  exactly  f  normal  strength  38  grams  of  stick  caustic 
soda  were  dissolved  in  2\  liters  of  water.  Ten  cc. 
of  this  solution  =  10.2  cc.  of  the  f  normal  hydrochloric 
acid  =  10.2  X  1.002  =  1 0.2  2  cc.  of  f  normal,  then  using  the 


CALCIUM  CARBONATE  IN  CEMENT          93 

/  b  \  (    IO.22  \ 

formula   f —  i  —  J  X  2,000  given  above,  {—         —  i  J  X 

2,000  =  22  cc.  of  water,  were  added  to  2  liters  (measured 
exactly)  of  the  alkali.  On  again  checking  against  the  hy- 
drochloric acid  10  cc.  acid  were  required  to  neutralize  10 
cc.  of  the  alkali. 

The  Iceland  spar  may  be  obtained  in  a  state  of  great 
purity,  and  is  very  well  suited  to  standardizing  the  solu- 
tions. If  the  chemist  has  reason  to  fear  impurities,  dis- 
solve i  or  2  grams  in  a  little  dilute  hydrochloric  acid, 
evaporate  to  dryness,  heat  the  residue  in  an  air-bath  at 
110°  C.  for  one  hour,  cool,  redissolve  in  a  little  dilute 
hydrochloric  acid  and  50  cc.  of  hot  water.  Filter,  wash, 
ignite,  and  weigh  the  residue  of  silica.  To  the  nitrate  add 
ammonia  in  slight  excess,  boil,  filter,  and  wash.  Ignite 
and  weigh  as  Fe2O  +  A12O  .  The  impurities  should  never 
exceed  a  few  milligrams  and  may  be  deducted  from  the 
weight  of  Iceland  spar.  The  difference  will  give,  of 
course,  the  weight  of  CaCO3,  and  this  multiplied  by  0.56 
the  weight  of  CaO. 

The  object  of  the  long  glass  tube  is  that  of  a  condenser 
to  catch  any  volatilized  acid.  If  it  is  rinsed  out  previous 
to  use  with  little  distilled  water  its  efficiency  is  increased. 

Instead  of  weighing  i  gram  of  the  cement  mixture,  the 
factor  weight  may  be  used.  That  is  such  a  weight  that 
each  cubic  centimeter  of  the  alkali  will  represent  a  per 
cent  of  CaO  in  the  sample.  To  find  this  weight  multiply 
the  value  of  each  cubic  centimeter  of  the  alkali  in  terms 


94 


ANALYTICAL  METHODS 


of  grams  of  CaO  by  100  ;  the  result  will  be  the  number  of 
grams  which  should  be  taken.     For  example,  suppose: 

50  cc.  acid  =  49. 1  cc.  alkali. 
50  cc.  acid  -f  0.5  gram  Iceland  spar  =  21.4  cc.  alkali. 

Then  0.5  gram  CaCO3  =  0.28  gram  CaO  =  49.1  —  21.4 
=  27.7  cc.  alkali,  and  i  cc.  alkali  ==  — —  =  o.oiou  gram 
CaO. 

Hence  if  we  take  o.oiou  X  100  =  i.on  grams  cement 
mixture  each  cubic  centimeter  of  alkali  will  be  equivalent 
to  i  per  cent  of  lime.  If  50  cc.  of  the  nitric  acid  were  used 
and  the  excess  of  acid  over  what  was  required  to  decom- 
pose the  i. 01 1  gram  of  cement  mixture  was  12.5  cc.,  then 
the  mixture  contains  49.1  —  12.5  =  36.6  per  cent  lime. 

By  Scheibler's  Calcimeter 

Fig.  17  shows  the  form  of  the  calcimeter.  It  consists 
of  the  following  parts  : 

A     arat          *'  ^  sma^  bottle,  A,  provided  with  a  perfo- 
rated stopper.     In  the  bottle  is  placed  a  tube, 
s,  of  gutta-percha  or  glass. 

2.  Another  bottle,  B,  provided  with  three  openings  in 
its  neck.  The  right-hand  opening  of  the  bottle  contains 
a  firmly  fixed  glass  tube  which  connects,  on  the  one  end 
with  A  by  means  of  the  flexible  rubber  tube,  r,  and  on  the 
other,  inside  of  the  bottle,  B,  with  a  very  thin  India-rubber 
bladder,  K.  The  left-hand  opening  is  controlled  by  a 
pinch-cock  on  a  piece  of  rubber  tubing  slipped  over  the 


CALCIUM  CARBONATE  IN  CEMENT 


95 


glass  tube,  q.  The  cen- 
tral opening  connects  B 
with  the  measuring 
tube. 

3.  An    accurately 
graduated   glass  cylin- 
der, C,  of  about  150  cc. 
capacity. 

4.  Another  glass  cyl- 
inder, D,  serving  to  reg- 
ulate the  pressure  of  the 
gas  measured  in  C. 

5.  A  water  reservoir, 
E,  consisting  of  a  two- 
necked  Woulff  bottle.  A 
glass    tube,   />,    passes 
through    a  stopper    in 
one  neck  nearly  to  the 
bottom  of  the  reservoir 
and  is  connected  with  D 
by  means  of  a  piece  of 
rubber  tubing.      The 
communication  be- 
tween D  and  E  is  con- 


Fig.  17. 


trolled  by  means  of  a  spring  clamp. 

The  whole  apparatus  with  the  exception  of  the  first  bot- 
tle, A,  is  fastened  to  a  suitable  stand  by  means  of  brass 
fittings  and  a  thermometer  is  also  attached. 

Open  the  spring  clamp,  p,  and  pour  distilled  water  into 


96  ANALYTICAL  METHODS 

D  by  means  of  a  funnel  until  the  bottle,  E,  is  nearly  full. 
When  ready  for  a  determination,  remove  the  stopper  from 
A,  open  the  spring  clamp,  p,  and  blow  air  into  v  from  the 
mouth  until  the  level  of  the  water  in  C  and  D  reaches  the 
zero  point  in  the  former.  Care  should  be  taken  not  to 
blow  the  water  into  the  tube,  u.  If  the  level  of  the  water 
passes  the  zero  mark  on  C,  it  may  be  brought  to  the  proper 
point  by  opening  the  spring  clamp,  p.  The  level  in  both 
tubes  should  be  the  same  and  stand  exactly  at  the  zero 
mark  in  C.  The  filling  of  the  tube,  C,  will  cause  the 
bladder,  K,  to  empty.  If  this  does  not  happen,  open  the 
clamp,  q,  and  blow  air  into  B  until  the  bladder  flattens. 
If  K  is  exhausted  before  C  is  filled  the  water  in  this  latter 
tube  will  stand  below  that  in  D  ;  in  this  case  also  open  q 
until  the  levels  are  the  same  and  at  the  zero  point  in  C. 

Place  in  the  bottle,  A,  a  weighed  quantity  of  the  dried 
slurry,  cement  mixture  or  limestone,  in  a  finely  powdered 
Th  D  condition.  Fill  the  cup,  s,  with  10  cc.  of 

mination  dilute  (i  :  i)  hydrochloric  acid  and  place  cau- 
tiously in  A  taking  care  not  to  spill  any  of 
the  acid  into  the  bottle.  Stopper  A  tightly,  greasing  the 
glass  stopper  with  a  little  tallow.  This  will  cause  the 
water  in  C  to  sink  and  in  D  to  rise  a  little.  Open  q  until 
the  levels  are  the  same;  close  and  note  the  thermometer  and 
barometer  reading.  Raise  the  bottle  and  tilt  it  slight!}' 
so  that  the  acid  in  s  runs  into  A,  and  graduall)'  mixes 
with  the  sample.  In  doing  this  hold  the  bottle  by  the 
neck,  to  avoid  warming,  with  the  right  hand  and  at  the 
same  time  regulate  p  with  the  left  so  that  the  water  in  the 


CALCIUM  CARBONATE  IN  CEMENT          97 

two  tubes  is  kept  at  the  same  height.  Continue  this  op- 
eration until  the  water  in  C  does  not  change  its  level  for 
a  few  seconds.  Now  bring  the  columns  of  water  in  C  and 
D  to  the  same  level  and  take  the  height  in  the  tube,  C, 
and  note  the  reading  of  the  thermometer  to  see  if  the  tem- 
perature has  remained  constant. 

It  is  necessary"  as  the  first  step  to  calculating  the  weight 
of  calcium  oxid  equivalent  to  the  volume  of  gas  given  off, 

to  correct  such  volume  for  temperature,  pres- 
Calculation 
of  Results      sure'         tension  of  aqueous  vapor  and  the  gas 

absorbed  or  held  back  by  the  hydrochloric 
acid.  This  latter  amounts  to  7  per  cent  of  the  volume  given 
off.1  To  make  the  necessary  corrections  use  the  formula 

•        V  =  z;X—  X 


—          —    —  -  __ 
93         V  i  +  0.00367  /         760 

in  which 

V  =  corrected  volume  (in  cc.) 
v  =  uncorrected  volume  (in  cc.) 
t  =  temperature,  C° 
p  =  pressure,  mm.  of  mercury 
^  =  tension  of  aqueous  vapor  at  t°  C.  as  given  in  the 

table  on  page  98. 

To  find  the  weight  of  V  cc.  of  carbon  dioxid,  multiply  V 
by  0.0019712,  the  weight  of  i  cc.  of  carbon  dioxid,  when 
measured  at  o°  C.  and  760  mm.  of  mercxiry  pressure.  To 
convert  this  weight  of  carbon  dioxid  to  its  equivalent  of 
lime,  CaO,  multiply  this  latter  result  by  1.2743;  or  to  con- 
vert to  calcium  carbonate,  CaCO3,  multiply  by  2.2743. 

1  Warrington  :  Chem.  News,  31,  253. 
7 


98 


ANALYTICAL  METHODS 


Or  :  Weight  of  CaO  =  0.002689  X  v      ^  0.00367  t  X    fr 
PENSION  OF  AQUEOUS  VAPOR 


t. 
Temp. 

5. 

Tension   in 
mm.  of 
mercury. 

Temp. 

Tension  in  |     -r^mi 
mm.  of               omp- 
mercury.     I 

Tension  in 
mm.  of 
mercury. 

10 

9.2 

18 

.5.4 

26 

25.0 

II 

-     9.8 

19 

I6.3 

27 

26.5 

12                  10.5                       20 

17.4 

28 

28.1 

13                  II.  2                       21 

18-5 

29 

29.8 

14                 Il.g                       22 

19.7 

30 

31.6 

15                  12.7                       23 

20.9 

31 

33-4 

16            13-5 

24 

22.2 

32 

35-4 

17 

14-4 

25 

23-5 

33 

37-4 

Notes 

Tables  are  usually  sold  with  these  instruments  which 
very  much  shorten  the  calculations,  a  graphic  table  such 
as  the  author  describes  in  his  "  Chemists'  Pocket  Manual" 
would  greatly  simplify  the  calculations  necessary  with  this 
instrument. 

The  above  corrections  for  the  volume  of  carbon  dioxid 
may  be  done  away  with,  by  making  a  determination  either 
with  a  standard  sample  of  sluny  or  cement  mixture  or 
with  pure  calcium  carbonate  (Iceland  spar)  before  each  series 
of  experiments  with  this  instrument.  If  the  temperature 
and  pressure  remain  the  same  during  the  time  for  the  series 
the  result  with  the  standard  sample  will  give  the  relation 


ANAL  YSIS  OF  CEMENT  MIXTURES  99 

between  the  volume  of  carbon  dioxid  and  the  weight  of 
lime.  For  example,  0.5  gram  of  finely  powdered  Iceland 
spar  (CaCO3)  was  weighed  out  and  the  volume  of  carbon 
dioxid  then  measured  and  found  to  be  111.5  cc-  °-7  gram 
of  the  slurry,  whose  percentage  of  lime  is  desired,  was  next 
weighed  out  and  the  volume  of  gas  found  to  be  116.5  cc. 
Now  0.5  gram  of  calcium  carbonate  is  equivalent  to  0.28 
gram  of  lime.  Then,  volume  of  gas  given  off  by  the  Iceland 
spar  :  that  given  off  by  the  slurry  : :  weight  of  lime  in 
Iceland  spar  :  that  in  the  slurry;  or  111.5  :  116.5  ::  °-28 
:  x  from  which  x  =  0.2927,  and  per  cent  of  lime  in  slurry 
=  0-2927  X  IPO 
0.7 

The  apparatus  should  be  placed  where  direct  sunlight 
cannot  fall  upon  it,  and  also  be  protected  from  any  heating 
apparatus,  such  as  radiator  or  stove,  or  Bunsen  burner.  It 
should  also  be  stood  near  a  North  window  so  as  to  have 
sufficient  light  for  reading  and  adjusting  the  water-levels. 

The  carbon  dioxid  in  the  slurry  may  also  be  determined 
by  means  of  the  apparatus  shown  on  page  76.  The  deter- 
mination is  carried  out  similar  to  that  of  carbon  dioxid  in 
cement,1  except  that  from  0.5  to  i  gram  of  slurry  is  suffi- 
cient for  a  sample.  The  loss  of  weight  multiplied  by 
1.2743  gives  the  lime  in  the  slurry. 

Complete  Analysis  of  Cement  Mixture  or  Slurry 

By  Fusion  with  Sodium  Carbonate 
Weigh  i  gram  of  the  finely  ground  dried  cement  mix- 

i  "  Rapid  Determination,"  page  76. 


ioo  ANALYTICAL  METHODS 

ture  or  slurry  into  a  large  platinum  crucible  and  mix  in- 
timately with  it  bv  stirring  with  a  smooth  well-rounded 
glass  rod  from  5  to  10  grams  of  sodium  car- 
bonate and  a  very  little  sodium  nitrate.  Cover 
the  crucible  and  heat  gently  at  first  over  a  low  Bunsen 
flame,  then  gradually  raise  the  latter  until  full  heat  is  at- 
tained. Next  heat  over  the  blast-lamp  until  the  contents 
of  the  crucible  are  in  quiet  fusion.  Run  the  fused  mass 
well  up  on  the  sides  of  the  crucible  and  chill  by  dipping 
the  bottom  of  the  latter  while  red  hot  into  a  basin  of  cold 
water.  When  cold  nearly  fill  the  crucible  with  hot  water 
and  set  on  the  hot  plate  for  a  little  while.  Pour  the  solu- 
tion, and  as  much  of  the  mass  as  becomes  detached  from 
the  crucible,  into  a  casserole  or,  better,  a  platinum  dish. 
Again  partly  fill  the  crucible  with  water,  and  after  digest- 
ing on  the  hot  plate  pour  into  the  dish.  Repeat  this  pro- 
cess until  the  mass  has  become  thoroughly  disintegrated. 
Half  fill  the  crucible  with  dilute  hydrochloric  acid,  heat 
and  pour  the  acid  into  the  casserole  or  dish,  keeping  as 
much  of  the  latter  as  possible  covered  bv  a  watch-glass  to 
avoid  loss  by  effervescence.  Clean  out  the  crucible  with 
a  rubber-tipped  rod,  and  after  acidifying  the  solution  in 
the  dish  evaporate  to  dryness.  Heat  the  dried  mass  in  an 
air-bath  at  110°  C.  for  one  hour,  or  on  the  hot  plate  or  air- 
bath  until  it  no  longer  gives  off  the  odor  of  h3'drochloric 
acid.  Cool,  moisten  the  dry  mass  with  a  few  drops  of  di- 
lute hydrochloric  acid  and  a  little  water  and  again  evapo- 
rate to  dryness.  Add  30  cc.  of  dilute  hydrochloric  acid, 


ANAL  YSIS  OF  CEMENT  MIXTURES  101 

digest  at  a  gentle  heat  for  a  few  minutes  and  add  100  to 
150  cc.  of  hot  water.  Allow  to  stand  a  little  while  on  the 
hot  plate  and  filter.  Wash  well  with  hot  water,  ignite 
over  a  Bunsen  burner  until  all  carbon  is  burned  off,  and 
then  over  a  blast-lamp  for  five  minutes.  Weigh  as  impure 
SiO2.  Moisten  the  contents  of  the  crucible  with  dilute 
sulfuric  acid  and  half  fill  the  crucible  with  hydrofluoric 
acid.  Evaporate  to  dryness  by  placing  over  a  burner  in 
an  inclined  position  in  such  a  way  that  a  low  flame  plays 
upon  the  underside  of  the  crucible  and  the  evaporation  takes 
place  only  from  the  surface.  Ignite  and  weigh.  The  dif- 
ference between  the  two  weights  is  silicon  dioxid,  SiO,.  If 
any  appreciable  residue  remains  in  the  crucible  dissolve  in 
a  little  concentrated  hydrochloric  acid  and  add  it  to  the 
filtrate  from  the  SiO^ 

Heat  the  filtrate  from  the  silica,  which  should  measure 
about  300  cc.  to  boiling,  and  add  ammonia  in  slight  but 
F  '  O  'd  distinct  excess ;  boil  for  a  few  minutes  and 
...  .  allow  the  precipitate  to  settle.  Filter  and 
-  wash  twice  with  boiling  water.  Remove  the 
filtrate  from  under  the  funnel  and  in  its  place  set  the 
beaker  in  which  the  ammonia  precipitation  was  made.  Dis- 
solve the  precipitate  of  iron  and  alumina  in  a  mixture  of 
15  cc.  of  dilute  hydrochloric  acid  and  15  cc.  of  cold  water, 
by  pouring  back  and  forth  through  the  filter  as  long  as 
any  precipitate  remains.  Wash  the  filter-paper  well  with 
cold  water,  dry,  place  in  a  weighed  platinum  crucible  and 
set  aside.  Reprecipitate  the  iron  and  alumina  in  the  solu- 


102  ANALYTICAL  METHODS 

tion  as  before  by  heating  to  boiling  and  adding  ammonia  in 
slight  but  distinct  excess.  Filter,  wash,  and  dry.  Brush 
the  precipitate  from  the  filter  upon  a  piece  of  glazed  paper 
with  a  camel's  hair  brush,  place  the  filter  in  the  crucible 
with  that  from  the  first  ignition  and  incinerate.  When 
all  the  carbon  is  burned  cool  the  crucible,  set  it  upon  an- 
other piece  of  glazed  paper  and  brush  the  precipitate  from 
the  first  paper  into  it.  Ignite  first  over  a  Bunsen  bur- 
ner and  then  over  a  blast-lamp  for  four  or  five  minutes. 
Cool  and  weigh  as  ferric  oxid  and  alumina,  Fe2O3  +  A1.,O3. 
To  determine  ferric  oxid  and  alumina  separately,  deter- 
mine the  ferric  oxid  in  this  precipitate  by  one  of  the 
methods  given  in  the  scheme  for  the  analysis  of  limestone, 
page  106,  and  deduct  from  the  weight  of  the  ferric  oxid 
and  alumina  combined.  The  difference  will  be  the  weight 
of  the  alumina,  A12O3. 

Heat  the  filtrate  from  the  iron  and  alumina  to  boiling 
and   add  30   cc.    of   a  saturated  solution    of    ammonium 

oxalate.  Stir  and  boil  for  a  few  minutes  and 
Linic* 

allow  to  stand  for  some  hours .  in  order  to 
allow  the  complete  precipitation  of  the  lime.  Filter  and 
wash  once  or  twice.  Dissolve  the  precipitate  in  a  little 
hydrochloric  acid,  wash  the  filter-paper  well  with  hot  water 
and  dilute  the  filtrate  to  500  cc.  Add  ammonia  to  strongly 
alkaline  reaction  and  then  a  little  more  ammonium  oxa- 
late. Heat  to  boiling.  Allow  to  settle  one  hour,  filter 
and  wash.  Dry  and  ignite  over  a  blast-lamp  until  the 
weight  is  constant.  Weigh  as  calcium  oxid,  CaO. 


ANAL  YSTS  OF  CEMENT  MIXTURES  103 

Make  the  first  filtrate  from  the  calcium  oxalate  precipi- 
tate slightly  acid  with  hydrochloric  acid,  and  add  30  cc. 

of  sodium  phosphate.  Evaporate  the  solu- 
Magnesia. 

tion  to  about  300  cc.  and  cool.  Add  ammo- 
nia drop  by  drop  from  a  burette  with  constant  stirring  un- 
til the  solution  is  slightly  alkaline  and  the  precipitate  be- 
gins to  form.  Stop  adding  ammonia  and  stir  for  five 
minutes,  then  add  one-tenth  the  volume  of  the  liquid  of 
strong  ammonia  and  stir  for  five  minutes  more.  Allow 
the  solution  to  stand  over  night  in  a  cool  place,  filter  and 
wash  with  a  mixture  of  1000  cc.  water,  500  cc.  ammonia 
(sp.  gr.  0.96),  and  150  grams  ammonium  nitrate.  Dry,  ig- 
nite (do  not  use  the  blast-lamp),  and  weigh  as  magnesium 
pyrophosphate,  Mg2P2O?.  Multiply  this  by  0.3619  for 
magnesium  oxid,  MgO. 

By  Ignition  with  Sodium  Carbonate 

Place  a  clean  dry  agate  mortar  upon  a  large  piece  of 
glazed  paper.  Weigh  roughly  into  it  0.5  gram  of  sodium 
carbonate,  and  after  grinding  this  finely, 
weigh  accurately  i  gram  of  the  finely  ground 
dried  cement  mixture  or  slurry  and  place  with  the  sodium 
carbonate  in  the  agate  mortar  upon  the  glazed  paper.  Mix 
thoroughly  by  grinding  and  then  transfer  the  contents  of 
the  mortar  to  an  ordinary  size  platinum  ignition  crucible. 
If  any  particles  of  the  mixture  have  fallen  upon  the  glazed 
paper  either  during  the  mixing  or  the  transferring  to  the 
crucible,  brush  them  also  into  the  crucible,  standing  the 
latter,  during  the  operation,  on  another  piece  of  glazed 


104  ANALYTICAL  METHODS 

paper.  Cover  the  crucible  with  its  lid  and  place  over  a 
Bunsen  flame  turned  very  low.  Gradually  raise  this  lat- 
ter until  the  crucible  is  at  a  red  heat.  Keep  at  this  tem- 
perature for  from  five  to  six  minutes,  and  then  heat  over 
a  good  blast-lamp  for  ten  or  fifteen  minutes.  This  treat- 
ment breaks  up  the  silicates  of  alumina  by  the  combined  ac- 
tion of  the  lime  in  the  cement  mixture  and  the  sodium  car- 
bonate at  the  high  temperature  of  the  blast-lamp,  to  form 
silicates  and  aluminates  of  calcium  and  sodium.  Cool  the 
crucible  while  still  hot,  by  dipping  in  a  basin  of  cold  water 
and  if  the  mass  is  in  the  form  of  a  solid  cake  and  loose 
from  the  crucible,  transfer  it  to  a  3^  inch  casserole.  Half 
fill  the  crucible  with  a  mixture  of  30  cc.  of  water  and  10 
cc.  of  dilute  hydrochloric  acid.  Heat  on  a  hot  plate  and 
then  pour  into  the  casserole,  covering  the  latter  with  a 
watch-glass.  Clean  out  the  crucible  with  a  rubber-tipped 
rod,  using  the  rest  of  the  mixture  of  acid  and  water.  To 
the  solution  in  the  casserole  add  a  few  drops  of  concen- 
trated nitric  acid,  evaporate  to  dryness  and  proceed  as  di- 
rected under  the  analysis  of  cements,  page  24. 

For  the  determination  of  sulfur  trioxid,  carbon  dioxid, 
combined  water,  and  alkalies,  refer  to  the  methods  given 
under  cement.  The  fusion  method  is  to  be  preferred  for 
determining  sulfur  trioxid. 


THE   ANALYSIS    OF    LIMESTONE 

Determination  of  Silica,   Fprric   Oxid,  and  Alu- 
mina, Lime,  and  Magnesia 

By  Ignition  of  the  Sample  with  Sodium  Carbonate 

Weigh  i  gram  of  finely  ground  dried  limestone  into  a 
platinum  crucible  and  mix  intimately  with  0.5  gram  of 
pure  dry  sodium  carbonate  by  stirring  with 
a  glass  rod.  Place  the  crucible  over  a  low 
flame  and  gradually  raise  this  latter  until  the  crucible  is 
red  hot.  Continue  heating  for  five  minutes,  then  substi- 
tute a  blast-lamp  for  the  Bunsen  burner  and  heat  for  five 
minutes  longer.  Place  the  crucible  in  a  dish  or  casserole, 
add  40  cc.  of  water  and  10  cc.  of  hydrochloric  acid,  and 
digest  until  air  the  mass  is  dissolved  out  of  the  crucible. 
Clean  off  the  crucible  inside  and  outside,  add  a  few  drops 
of  nitric  acid  to  the  solution  and  evaporate  it  to  dryness. 
Heat  the  residue  at  110°  C.  for  one  hour,  cool,  add  15  cc. 
of  dilute  hydrochloric  acid,  cover  with  a  watch-glass  and 
digest  for  a  few  minutes  on  the  hot  plate.  Dilute  with  50 
cc.  of  hot  water,  heat  nearly  to  boiling,  and  filter.  Wash 
the  residue  well  with  hot  water.  Dry,  ignite,  and  weigh 
as  silica,  SiO2. 

Heat  the  filtrate  to  boiling,  add  ammonia  in  slight  but 
distinct  excess,  boil  for  five  minutes  and  filter.  Wash  the 


106  ANALYTICAL  METHODS 

precipitate  twice  with   hot  water.      Remove  the   filtrate 
from  under  the  funnel  and  in  its  place  .stand  the  beaker 
in  which  the  precipitation  was  made.     Dis- 
solve the  precipitate  in  dilute  hydrochloric 
Alumina         ac^  an(^  wasn  t^ie  filter-paper  free  from  iron 
with  cold  water.     Heat  the  solution  to  boiling 
and  precipitate  the  iron  and  alumina  with  ammonia  as  be- 
fore.    Filter,   allowing  the  filtrate  to  run  into  that  from 
the  first  precipitation,  wash  well  with  hot  water,  dry  and 
ignite.     Weigh  and  report  as  ferric  oxid  and  alumina. 

If  the  percentage  of  ferric  oxid  and  alumina  are  desired 
separately,  proceed  as  directed  in  A,  B,  or  C. 

A.  Fuse  the  precipitate  of  ferric  oxid  and  alumina,  after 
weighing,  with  a  little  sodium  carbonate,  dissolve  in  a  lit- 
tle water  to  which  a  few  cubic  centimeters  of  hydrochloric 
acid  have  been   added,  and  drop  into  the  solution  a  few 
small  crystals  of  citric  acid.     Add  ammonia  until  the  solu- 
tion smells  slightly  of  the  reagent,   and   then  an    excess 
of  ammonium  sulfid.     Allow  the  black  precipitate  to  set- 
tle,  filter,  wash  a  few  times,  dissolve  in  hydrochloric  acid, 
add  a  little  bromin  water,  boil  a  \^hile  and  add  ammonia 
in  slight  but  distinct  excess.     Filter,   wash  well  with  hot 
water,  ignite  and  weigh  as  Fe2O3.     Deduct  this  weight 
from  that  of  the  total  ferric  oxid  and  alumina,   for  the 
weight  of  alumina,  AlaO3. 

B.  Fuse  the  precipitate  of  ferric  oxid  and  alumina,  after 
weighing,  with  caustic  potash  in  a  silver  crucible  or  dish. 
Treat  the  fusion  with  water,  boil,  filter,  and  wash.     Dry, 


ANAL  YSIS  OF  LIMESTONE  107 

ignite,  and  weigh  the  residue  as  ferric  oxid,  Fe2O3.  Deduct 
this  weight  from  that  of  the  ferric  oxid  and  alumina,  for 
the  weight  of  alumina,  A12O  . 

C.  Dissolve  the  residue,  after  fusion  with  sodium  car- 
bonate, in  a  little  dilute  hydrochloric  acid  and  determine 
the  ferric  oxid  volumetrically  by  the  method  given  on 
page  49. 

Heat  the  filtrate  from  the  iron  and  alumina,  which  should 

measure  between  750  and   1000  cc.,  to  boiling  and  add  25 

cc.  of  a  saturated  solution  of  ammonium  oxa- 

late.     Stir  and  boil  for  a  few  minutes  and 

allow  the  precipitate  one  hour  in  which  to  settle.     Filter 

and  wash  well  with  hot  water.     After  washing,  treat  the 

precipitate  as  directed  below  in  A,  B,  or  C. 

A .  Dry  the  precipitate  by  heating  over  a  low  flame,  in 
a  weighed  platinum  crucible,  ignite  until  all  carbonaceous 
matter  is  destroyed  and  ignite  for  fifteen  minutes  over  a 
blast-lamp.     Cool  and  weigh.     Again  ignite  for  five  min- 
utes over  a  blast-lamp  and  weigh.     If  this  weight  agrees 
to  within  0.0002  gram  of  the  former  one  it  may  be  taken 
as  the  weight  of  the  calcium  oxid,  CaO.     If  it  does  not 
agree,   ignite  again  and  repeat,   if  necessary,    until   the 
weight  is  constant. 

B.  Punch  a  hole  in  the  filter-paper  and  wash  the  pre- 
cipitate into  the  beaker  in  which  the  precipitation  was 
formed.     Wash  the  paper  with  dilute  sulfuric  acid  from  a 
wash-bottle  and  then  with  hot  water.     Dilute  the  solution 
to  300  or  400  cc.,  heat  to  60°  or  70°  C.,  and  after  adding  10 
cc.  of  dilute  sulfuric  acid  titrate  with  permanganate.  Cal- 


io8  ANALYTICAL  METHODS 

culate  the  per  cent  of  lime,  CaO,  or  calcium  carbonate, 
CaCO  ,  in  the  limestone,  as  directed  under  ' '  Volumetric 
Determination  of  Calcium,"  page  40. 

C.  Dry  the  precipitate  thoroughly,  remove  it  as  far  as 
possible  from  the  filter-paper  to  a  piece  of  black  glazed 
paper.  Burn  the  filter-paper  in  a  weighed  crucible.  Cool 
and  add  the  precipitate.  Drop  concentrated  sulfuric  acid 
on  the  contents  of  the  crucible  until  it  is  well  mois- 
tened. Avoid  adding  an  excess.  Heat  the  crucible  under 
a  hood  cautiously  from  a  burner  held  in  the  hand  until 
the  swelling  of  the  mass  ceases,  and  the  excess  of  sulfuric 
acid  is  driven  off.  This  happens  when  white  fumes  cease 
to  come  from  the  crucible.  Heat  the  crucible  now  for  five 
minutes  to  a  cherry-red  heat,  but  do  not  use  the  blast- 
lamp.  Cool  and  weigh  as  calcium  sulfate,  which  multi- 
plied by  0.41185  gives  the  equivalent  of  lime,  CaO,  or  by 
0.73504  that  of  calcium  carbonate,  CaCO3. 

To  the  filtrate  from  the  calcium  oxalate  add  sufficient 
hydrochloric  acid  to  make  it  slightly  acid,  and  30  cc.  of 
.  sodium  phosphate.  Concentrate  to  about  300 
cc.  by  evaporation.  Set  the  solution  in  a 
vessel  of  cold  water  and  when  cooled  to  the  temperature 
of  the  latter  add  ammonia,  drop  by  drop,  from  a  burette, 
with  constant  stirring  until  slightly  ammoniacal  and  the 
precipitate  begins  to  form.  Stop  adding  ammonia  and 
stir  for  five  minutes,  add  one-tenth  the  volume  of  the  liquid 
of  strong  ammonia  and  continue  the  stirring  for  three 
minutes  more.  Allow  the  solution  to  stand  in  a  cool  place 


ANAL  YSIS  OF  LIMESTONE  109 

over  night,  filter,  wash  well  with  a  mixture  of  1000  cc.  wa- 
ter, 500  cc.  ammonia  (sp.  gr.  0.96),  and  150  grams  ammo- 
nium nitrate.  Dry,  ignite,  and  weigh  as  magnesium  pyro- 
phosphate,  Mg2P2O7.  Multiply  this  by  0.36190  for  its 
equivalent  of  magnesia,  MgO,  or  by  0.75722  for  magne- 
sium carbonate,  MgCO  . 

By  Solution  in  Hydrochloric  Acid 

Weigh  i  gram  of  the  finely  ground  dried  limestone  into 
a  porcelain  dish  or  casserole,  cover  with  a  watch-glass  and 

Insolubl  a<^  3°  CC'  °^  water  an^  I0  cc'  °^  concentrated 

Silicious  hydrochloric  acid.  Warm  until  all  efferves- 
Matter  cence  has  ceased,  uncover,  add  a  few  drops  of 

nitric  acid,  and  evaporate  to  dryness.  Bake 
on  the  hot  plate  or  sand-bath  until  all  odor  of  hydrochlo- 
ric acid  has  disappeared,  or  safer  still,  heat  in  an  air-bath 
at  110°  C.  for  one  hour  after  the  residue  has  become  per- 
fectly dry.  Cool  the  dish  and  add  5  cc.  of  dilute  hydro- 
chloric acid,  set  on  the  hot  plate,  covered  with  a  watch- 
glass  for  five  minutes,  then  add  50  cc.  of  hot  water  and 
filter,  after  digesting  until  all  except  silicious  matter  dis- 
solves. Wash  thoroughly,  ignite  and  weigh  as  "insolu- 
ble silicious  matter." 

Should  it  be  desirous  to  know  the  silica  in  the  ' '  insolu- 
ble silicious  matter  ' '   fuse  it  with  ten  times  its  weight  of 
pure  dry  sodium  carbonate,  first  over  a  Bun- 
sen  burner  turned  low,  and  then,  after  slowly 
raising  the  flame  of  this  latter  to  its  full  height,  over  a 
blast-lamp  until  the  contents  of  the  crucible  are  in  a  state 


i io  ANALYTICAL  METHODS 

of  quiet  fusion.  Remove  the  crucible  from  the  lamp  and 
run  the  fused  mass  well  up  on  its  sides  by  tilting  and  re- 
volving the  crucible  while  held  with  the  crucible  tongs. 
While  still  hot  dip  the  crucible  three-quarters  of  the  way 
up  in  a  pan  of  cold  water  which  will  frequently  cause  the 
mass  to  loosen  from  the  crucible.  Wash  off  any  material 
spattered  on  the  crucible  cover  into  a  casserole  or  dish  with 
hot  water,  and  add  the  mass  in  the  crucible  if  it  has  become 
detached.  If  not,  fill  the  crucible  with  hot  water  and  set 
on  the  hot  plate  until  the  fused  mass  softens  and  can  be 
removed  to  the  casserole.  Dissolve  any  particles  of  the 
mass  in  hydrochloric  acid,  that  adhere  too  firmly  to  the 
crucible  to  be  removed  by  gentle  rubbing  with  a  rubber- 
tipped  rod.  When  the  hot  water  has  thoroughly  disinte- 
grated the  fused  mass,  cover  the  casserole  or  dish  with  a 
watch-glass  and  strongly  acidify  the  contents  with  hydro- 
chloric acid.  Heat  until  all  effervescence  ceases  and  every- 
thing dissolves  except  the  silica.  Wash  off  the  watch- 
glass  into  the  dish  and  evaporate  the  solution  to  dryness. 
Heat  for  one  hour  at  110°  C.  in  an  air-bath,  or  on  the  hot 
plate  at  not  too  high  a  temperature  until  all  odor  of  hydro- 
chloric acid  has  disappeared  from  the  dry  mass.  Cool, 
add  io  cc.  of  hydrochloric  acid  and  50  cc.  of  water,  warm 
until  all  soluble  salts  are  in  solution,  filter,  wash  well 
with  hot  water,  dry,  ignite,  and  weigh  as  silica,  SiO2. 

Mix  the  two  filtrates  from  the  silica  separations  and  pro- 
Fe  O  Al  O    °eec*   to  Determine   *ron   an(i   alumina,    lime 
^ '  atl(*  magnesia.  as  directed  in  the  method  "By 
Ignition  with  Sodium  Carbonate. ' ' 


ANALYSIS  OF  LIMESTONE  ixi 

When  the  amount  of  sodium  carbonate  added  to  the 
"insoluble  silicious  matter"  is  greater  than  0.5  gram,  it 
is  best  in  very  accurate  work,  instead  of  mixing  the  two 
filtrates  from  the  silica,  to  determine  the  iron,  alumina, 
lime,  and  magnesia  in  each  solution  separately,  since 
the  large  lime  precipitate  is  almost  sure  to  be  contamina- 
ted with  sodium  salts  if  the  two  filtrates  are  mixed. 

Determination  of  Organic  Matter,  Insoluble  Sili- 
cious Matter,  Ferric  Oxid  and  Alumina, 
Lime  and  Magnesia 

Weigh  i  gram  of  the  finely  ground  dried  limestone  into 
a  porcelain  dish  or  casserole ;  cover  with  a  watch-glass  and 
.  add  30  cc.  of  water  and  10  cc.  of  concentrated 

--  hydrochloric  acid.  Warm  until  all  efferves- 

cence ceases,  uncover  and  evaporate  to  dry- 
ness  on  a  water-bath.  Heat  the  dish  for  one  hour,  after 
the  residue  becomes  thoroughly  dry,  at  110°  C.  in  an  air- 
bath.  Cool  the  dish  and  add  5  cc.  of  hydrochloric  acid 
and  50  cc.  of  hot  water.  Heat  until  all  soluble  salts  dis- 
solve, filter  upon  a  Gooch  crucible  or  a  small  counterpoised 
filter-paper.  Wash  well  with  hot  water,  dry  at  100°  C.  in 
an  air-bath  and  weigh  as  "organic  matter  "  plus  "insolu- 
ble silicious  matter. ' ' 

Now  ignite  until  all  carbonaceous  matter  is  destroyed, 
and  cool  and  weigh  as  ' '  insoluble  silicious  matter. ' '  This 
weight  subtracted  from  the  preceding  one  gives  the  ' '  or- 


ii2  ANAL  YTICAL  ME THODS 

ganic  matter. "     If  the  silica  in  the   "insoluble  silicious 
matter' '  is  desired,  fuse  the  latter  with  ten  times  its  weight 
of  sodium  carbonate  and  proceed  as  described 
QT  •  in  the  preceding  scheme  for  the  analysis  of 

Matter  limestone     "By    Solution    in    Hydrochloric 

Acid." 

Heat  the  filtrate  from  the  "organic  matter"   and  the 
"insoluble   silicious  matter"   to  boiling, 
CaO  ''M   O  3>      a<^   ammonia  in  slight   but   distinct   ex- 
cess,  and  proceed  to  determine  the  ferric 
oxid  and  alumina,   lime  and  magnesia,   as   directed   on 
page  105. 

The   Determination   of  Alkalies,    Sulfuric    Acid, 
Carbon  Dioxid,  Combined  Water  and 

Loss  on  Ignition 

For  the  determination  of  these  constituents  refer  to  the 
methods  given  under  cement. 


METHODS  FOR  THE  ANALYSIS  OF  CLAY 


Determination  of  Silica,  Ferric  Oxid,   Alumina, 
Lime  and  Magnesia 

Finely  grind  the  sample  of  clay  and  heat  at  100°  to  1 10° 
C.  for  one  hour  in  an  air-bath.  Transfer  i  gram  of  the 
Silica  dried  clay  to  a  fairly  large  platinum  crucible. 

Mix  with  it  by  stirring  with  a  smooth  glass 
rod  10  grams  of  sodium  carbonate  and  a  little  sodium  ni- 
trate. Heat  over  a  Bunsen  burner,  gently  at  first,  for  a 
few  minutes  and  then  to  quiet  fusion  over  a  blast-lamp. 
Run  the  fused  mass  well  up  on  the  sides  of  the  crucible 
and  allow  to  cool.  Nearly  fill  the  crucible  with  hot  water 
and  set  on  the  hot  plate  for  a  few  minutes.  Pour  the  solu- 
tion and  as  much  of  the  mass  as  has  become  detached  from 
the  crucible  into  a  casserole  or  better  a  platinum  dish. 
Repeat  this  treatment  until  the  mass  has  become  thor- 
oughly disintegrated.  Treat  what  remains  in  the  cruci- 
ble with  dilute  hydrochloric  acid  and  pour  the  acid  into 
the  casserole  or  dish.  Clean  out  the  crucible  with  a  rubber- 
tipped  rod  and  after  acidify  ing  with  hydrochloric  acid  evap- 
orate the  contents  of  the  casserole  to  dryness.  Heat  in  an 
air-bath  at  110°  C.  for  one  hour,  or  until  all  odor  of  hy- 
drochloric acid  has  vanished.  Cool,  moisten,  the  mass 
with  dilute  hydrochloric  acid,  add  a  little  water  and  again 
evaporate  to  dryness.  Now  add  30  cc.  of  dilute  hydro- 
chloric acid,  digest  at  a  gentle  heat  for  a  few  moments  and 


ii4  ANALYTICAL  METHODS 

add  100  to  150  cc.  of  hot  water.  Allow  to  stand  a  few 
minutes  on  the  hot  plate  and  filter.  Wash  the  residue 
thoroughly  with  hot  water,  ignite  over  a  Bunsen  burner 
until  all  carbon  is  burned  off,  and  then  for  five  minutes 
over  a  blast-lamp,  and  weigh  as  impure  silica.  Moisten 
the  silica  with  a  few  drops  of  dilute  sulfuric  acid  and  half 
fill  the  crucible  with  hydrofluoric  acid.  Evaporate  to  dry- 
ness  by  placing  over  a  burner  in  an  inclined  position  so 
that  the  low  flame  plays  upon  the  side  of  the  crucible  and 
the  evaporation  takes  place  only  from  the  surface.  Ignite 
and  weigh.  The  difference  between  the  two  weights  is 
the  silicon  dioxid,  SiO3.  If  any  appreciable  residue  re- 
mains in  the  crucible  dissolve  it  in  a  little  concentrated 
hydrochloric  acid  and  add  it  to  the  filtrate  from  the  silica. 
Heat  the  filtrate  from  the  silica,  which  should  measure 
about  300  cc.,  to  boiling,  and  add  ammonia  in  slight  but 

distinct  excess ;  boil  for  a  few  moments  and 
and  allow  the  precipitate  to  settle.  Filter  and 

Alumina.  wash  several  times  with  hot  water.  Remove 

the  filtrate  from  under  the  funnel  and  dis- 
solve the  precipitate  of  iron  and  alumina  in  a  mixture  of 
15  cc.  of  dilute  hydrochloric  acid  and  15  cc.  of  cold  water, 
by  pouring  back  and  forth  through  the  filter  as  long  as 
any  precipitate  remains.  Wash  the  filter-paper  well  with 
cold  water,  dry,  place  in  a  weighed  platinum  crucible,  and 
set  aside.  Reprecipitate  the  iron  and  alumina  in  the 
filtrate  as  before  by  adding  a  slight  but  distinct  excess  of 
ammonia,  filter,  and  wash  thoroughly  with  hot  water.  Dry, 
transfer  the  precipitate  from  the  filter  to  a  piece  of  glazed 


ANAL  YSfS  OF  CLA  Y  1 15 

paper  with  a  camel's  hair  brush,  place  the  filter  in  the 
crucible  with  the  other  filter-paper  and  ignite  until  all 
carbon  is  burned,  cool  the  crucible,  set  it  upon  another 
piece  of  glazed  paper  and  brush  the  precipitate  from  the 
first  paper  in  with  the  filter  ash,  ignite  first  over  a  Bunsen 
burner  and  then  strongly  over  a  blast-lamp  for  four  or  five 
minutes.  Cool  and  weigh  as  ferric  oxid  and  alumina.  De- 
termine the  ferric  oxid  in  the  precipitate  as  in  A  or  B  below 
and  subtract  the  amount  from  this  weight  ;  the  difference 
will  be  the  alumina. 

A.  Fuse  the  ignited  precipitate  with  sodium  carbonate, 
treat  the  fused  mass  with  hot  water  and  wash  it  out  into 
a  small  beaker,  allow  the  residue  to  settle  and  decant  off 
the  clear  supernatant  liquid  through  a  small  filter,  leaving 
the  residue  in  the  bottom  of  the  beaker.     Wash  the  filter- 
paper  once  and  pour  a  little  hot  concentrated  hydrochloric 
acid  through  the  filter  into  the  beaker  containing  the  resi- 
due.    Heat  gently,  but  do  not  boil.     When  all  the  residue 
is  dissolved,  determine  the  iron  in  the  precipitate  by  reduc- 
tion with  stannic  chlorid   and  titration  with  potassium 
bichromate  as  directed  on  page  49. 

B.  Brush  the  ignited  precipitate  into  a  small  beaker, 
cover  with  a  mixture  of  6  cc.  of  water  and  16  cc.  of  con- 
centrated sulfuric  acid,  and  covering  with  a  watch-glass, 
digest  on  a  hot  plate  or  sand-bath  until  all  dissolves,  ex- 
cept possibly  a  residue  of  silica.     Filter,  if  necessary,  and 
determine  the  iron  by  reduction  with  zinc  and  titration 
with  standard  permanganate  as  directed  on  page  53. 

Heat  the  filtrate  from   the  iron  and  alumina  to  boiling 


n6  ANALYTICAL  METHODS 

and  add  an  excess  of  a  saturated  solution  of  ammonium 
oxalate.     Stir  and  boil  for  a  few  minutes  and  set  aside 
for  several  hours  to  allow  the  complete  pre- 
cipitation of  the  lime.     Filter,  wash,  dry,  and 
ignite  over  a  blast-lamp  until   the  weight  is  constant. 
Weigh  as  calcium  oxid,  CaO. 

To  the  filtrate  from  the  calcium  oxalate  add  sufficient 
hydrochloric  acid  to  make  it  slightly  acid  and  then  30  cc. 
.  of  sodium  phosphate.  Concentrate  the  solu- 
tion to  about  300  cc.  by  evaporation  and  cool. 
Then  add  ammonia  drop  by  drop  from  a  burette,  with  con- 
stant stirring  until  the  liquid  is  slightly  ammoniacal  and 
the  precipitate  begins  to  form.  Stop  adding  ammonia 
and  stir  for  five  minutes,  then  add  one-tenth  the  volume 
of  the  liquid  of  strong  ammonia  and  continue  the  stirring 
for  five  minutes  more.  Allow  the  solution  to  stand  in  a 
cool  place  over  night,  filter,  wash  with  a  mixture  of  1000 
cc.  water,  500  cc.  ammonia  (sp.  gr.  0.96),  and  150  grams 
ammonium  nitrate.  Dry,  ignite  (do  not  use  the  blast- 
lamp),  and  weigh  as  magnesium  pyrophosphate,  Mg2P2O  . 
Multiply  this  by  0.36190  for  magnesium  oxid,  MgO. 

Notes 

Clay  is  practically  unacted  upon  by  hydrochloric  acid 
and  requires  fusion  with  alkaline  carbonates  for  its  de- 
composition. 

Should  the  solution,  on  evaporation  to  dry  ness,  show  a 
tendency  to  climb  the  sides  of  the  dish,  greasing  the  latter 
lightly  with  vaseline  or  paraffine  will  remove  the  difficulty. 


ANA L  YSIS  OF  CLAY  117 

Mr.  Thos.  A.  Hicks,  of  the  Art  Portland  Cement  Co., 
Sandusky,  O.,  adopts  the  following  method  of  fusion  and 
solution  where  clays  and  slurries  are  under  examination : 
One  gram  of  the  sample  is  fused  with  about  ten  times  its 
weight  of  a  mixture  of  potassium  and  sodium  carbonates 
(i  :  i)  in  a  platinum  crucible  over  a  blast-lamp.  More  of 
the  fusion  mixture  is  added  and  fused  a  little  at  a  time 
until  the  crucible  is  one-half  full  of  the  fused  mass.  The 
crucible  and  contents  are  cooled  by  dipping  in  water  and 
then  dropped  with  the  mouth  downward  on  an  iron  plate 
covered  with  glazed  paper.  The  fused  mass  is  thus  easily 
removed  from  the  crucible.  The  mass  is  now  brushed 
from  the  glazed  paper  into  an  evaporating  dish  and  dis- 
solved in  dilute  hydrochloric  acid.  The  top  of  the  dish  is 
greased  with  vaseline  to  prevent  ' '  climbing ' '  of  the  con- 
tents and  the  solution  evaporated  to  dryness,  after  which 
it  is  heated  at  110°  C.  in  an  air-bath  until  all  free  hydro- 
chloric acid  is  driven  off.  The  resulting  mass  is  redis- 
solved  in  water  and  dilute  hydrochloric  acid  and  the  anal- 
ysis completed  as  above,  except  that  in  the  analysis  of 
clay  the  precipitate  of  calcium  oxalate  is  allowed  to  stand 
over  night  in  order  to  secure  as  complete  a  separation  as 
possible,  and  then  titrated  with  standard  permanganate. 

The  amounts  of  lime  and  magnesia  in  clays  are  small, 
so  that  the  filtrate  and  washings  from  the  second  ammo- 
nia precipitation  of  the  iron  and  alumina  may  be  rejected 
and  the  lime  and  magnesia  determined  in  the  first  filtrate 
only.  For  the  same  reason  it  is  unnecessary  to  reprecipi- 
tate  the  calcium  oxalate,  although  the  solution  is  largely 
contaminated  by  sodium  salts  from  the  alkaline  fusion. 


n8  ANALYTICAL  METHODS 

Determination  of  Free,  Hydrated  and  Combined 
Silica1 

To  ascertain  how  much  of  the  silica  found  exists  in  com- 
bination with  the  bases  of  the  clay,  how  much  as  hydrated 
acid,  and  how  much  as  quartz  sand  or  as  a  silicate  present 
in  the  form  of  sand,  proceed  as  follows  :z 

Let  A  represent  silica  in  combination  with  the  bases  of 
the  clay. 

Let  B  represent  hydrated  silicic  acid. 

Let  C  represent  quartz  sand  and  silicates  in  the  form  of 
sand,  e.  g.,  feldspar  sand. 

Dry  2  grams  of  the  clay  at  a  temperature  of  100°  C., 
heat  with  sulfuric  acid,  to  which  a  little  water  has  been 
added,  for  eight  or  ten  hours,  evaporate  to  dryness,  cool, 
add  water,  filter  out  the  undissolved  residue,  wash,  dry, 
and  weigh  (A  +  B  -f  C).  Then  treat  it  with  sodium  car- 
bonate. Transfer  it,  in  small  portions  at  a  time,  to  a  boil- 
ing solution  of  sodium  carbonate  contained  in  a  platinum 
dish,  boil  for  some  time  and  filter  off  each  time,  still  very 
hot.  When  all  is  transferred  to  the  dish,  boil  repeatedly 
with  strong  solution  of  sodium  carbonate  until  a  few  drops 
of  the  liquid  finally  passed  through  the  filter  remain  clear 
on  warming  with  ammonium  chlorid.  Wash  the  residue, 
first  with  hot  water,  then  (to  insure  the  removal  of 
every  trace  of  sodium  carbonate  which  may  still  adhere 
to  it)  with  water  slightly  acidified  with  hydrochloric  acid, 
and  finally  with  water.  This  will  dissolve  (A  +  B)  and 

1  Cairns'  "  Quantitative  Chemical  Analysis,"  page  68. 

2  Compare  Fresenius'  "Quantitative  Analysis,  "  5th  ed.,  1865,  g  236. 


ANAL  YSIS  OF  CLAY  119 

leave  a  residue  (C)  of  sand,  which  dry,  ignite,  and  weigh. 

To  determine  (B),  boil  -4  or  5  grams  of  clay  (previously 
dried  at  100°  C.)  directly  with  a  strong  solution  of  sodium 
carbonate  in  a  platinum  dish  as  above,  filter  and  wash 
thoroughly  with  hot  water.  Acidify  the  filtrate  with  hy- 
drochloric acid,  evaporate  to  dryness,  and  determine  the 
silica  as  usual.  It  represents  (B)  or  the  hydrated  silicic 
acid. 

Add  together  the  weights  of  (B)  and  (C),  thus  found, 
and  subtract  the  sum  from  the  weight  of  the  first  residue 
(A  +  B  +  C).  The  difference  will  be  the  weight  of  (A) 
or  the  silica  in  combination  with  the  bases  of  the  clay. 

If  the  weight  of  (A  +  B  +  C)  found  here  be  the  same 
as  that  of  the  silica  found  by  fusion  in  a  similar  quantity 
in  the  analysis  of  the  clay,  the  sand  is  quartz,  but  if  the 
weight  of  (A  +  B  +  C)  be  greater,  then  the  sand  contains 
silicates. 

The  weight  of  the  bases  combined  with  silica  to  form 
silicates  can  be  found  by  subtracting  the  weight  of  total 
silica  found  in  i  gram  in  the  regular  analysis,  from  the 
weight  of  (A  +  B  +  C)  in  i  gram. 

Notes 

The  following  scheme  is  much  less  trouble  than  that 
described  above  and  gives  the  silica  present  as  sand  and 
silicates  undecomposable  by  sulfuric  acid  and  that  in  com- 
bination with  the  alumina  or  combined  silica. 

Heat  1.25  grams  of  the  finely  ground  and  dried(at  100°  C.) 
clay  with  15  cc.  of  concentrated  sulfuric  acid  to  near  the 


120  ANALYTICAL  METHODS 

boiling-point  of  the  acid  and  digest  for  from  ten  to  twelve 
hours  at  this  temperature.  Cool,  dilute  and  filter.  Wash 
and  ignite  the  residue  to  a  constant  weight.  Call  this 
weight  A.  After  weighing  brush  the  residue  which  con- 
sists of  silica  present  as  sand  and  undecomposable  silicates 
and  silica  from  the  decomposition  of  the  silicates  of  alu- 
mina, into  an  agate  mortar,  grind  very  finely  and  weigh  0.5 
gram  of  it  into  a  platinum  dish  containing  50  cc.  of  boil- 
ing caustic  potash  solution  (of  1.125  SP-  &r-)-  Boil  for  five 
minutes,  filter,  wash,  first  with  hot  water  and  then  with 
water  containing  a  little  dilute  hydrochloric  acid  and  then 
again  with  hot  water,  dry  and  ignite  to  a  constant  weight. 
Call  this  weight  B.  Multiply  A  by  0.4  (to  correct  the 
1.25  grams  of  clay  used  to  correspond  to  the  0.5  gram  of  the 
residue  taken  for  treatment  with  caustic  potash  solution) 
and  subtract  B  from  the  product.  Multiply  the  difference 
by  200  for  the  per  cent  of  silica  combined  with  alumina  in 
the  clay.  This  deducted  from  the  total  silica  found  by 
analyses  gives  the  silica  as  sand  and  undecomposable 
silicates. 

Determination  of  Water  of  Combination 
Should  the  clay  contain  very  little  organic  matter,  iron 
pyrites  or  calcium  carbonate,  heat  i  gram  of  the  previously 
dried  cement  for  twenty  minutes  to  a  bright  redness  over 
a  Bunsen  burner.  The  loss  in  weight  will  represent  the 
water  of  combination.  If,  however,  the  clay  contains 
much  organic  matter,  calcium  carbonate  or  iron  pyrites, 
the  wear  of  combination  should  be  determined  by  absorp- 


ANAL  YSIS  OF  CLA  Y  121 

tion  in  a  weighed  calcium  chlorid  tube  as  described  for 
cement  analysis  on  page  64. 

Note 

If  calcium  carbonate  is  present,  weigh  i  gram  of  clay 
into  a  beaker,  add  50  cc.  of  water  and  2  or  3  cc.  of  dilute 
hydrochloric  acid.  Warm  gently  until  the  carbon  dioxid 
is  expelled  and  filter  through  a  weighed  Gooch  crucible 
and  felt,  or  upon  a  previously  weighed  ashless  filter.  Wash, 
dry  for  two  hours  at  100°  to  105°  C.  and  weigh.  Ignite 
the  filter  and  residue  strongly  and  again  weigh.  The  loss 
represents  water  of  combination  (and  organic  matter  if 
present).  If  a  filter-paper  has  been  used  its  weight  should 
of  course  be  added  to  the  weight  of  residue  after  ignition 
before  subtraction. 

Many  chemists  simply  heat  i  gram  of  dried  clay  over  a 
blast  for  twenty  minutes  reporting  the  loss  of  weight  as 
loss  on  ignition.  This  loss,  of  course,  comes  from  co.m- 
bined  water  and  carbon  dioxid  driven  off  (from  the  decom- 
position of  carbonates),  organic  matter  burned  and  iron 
pyrites  changed  from  iron  sulfid,  FeS2,  to  ferric  oxid. 

Sulfur  and  Iron  Pyrites 

For  the  determination  of  sulfur  in  clay,  proceed  as  di- 
rected for  determining  this  constituent  in  cements  by  fu- 
sion with  sodium  carbonate  and  potassium  nitrate.  Mul- 
tiply the  weight  of  barium  sulfate  by  0.25845  and  report 
as  iron  pyrites,  FeS,,,  or  by  0.13734  and  report  as  sulfur. 


PHYSICAL  METHODS 

SPECIFIC  GRAVITY 

The  specific  gravity  of  cement  is  usually  taken  by  means 
of  Le  Chatelier's  apparatus,  which  has  lately  been  recom- 
mended  by  the  French  Commission  des  Me- 
«,    t  ..    ,       thodes  d'Essai  des  Mate"riaux  de  Construction. 
Apparatus.    Referring  to  Fig.  18  it  will  be  seen  to  consist 
of  a  flask  of  80  cc.   capacity,  having  a  neck 
about  20  cm.  long  and  about  9  mm.  in  diameter.     About 
half  way  up  the  neck  is  a  bulb  of  exactly  20  cc. 
capacity  between  the  marks  indicated  in  the 
illustration.       Commencing   at   the   upper   of 
these  two  marks,  the  tube  is  graduated  from 
o  to  5  cc.  in  tenths  of  a  cubic  centimeter.     The 
method  of  using  the  apparatus  is  as  follows  : 
The  flask  is  filled  to  the  lower  mark  of  the  20 
cc.  bulb  with  paraffin,  turpentine  or  benzine. 
This  latter  should  be  free  from  water  and  not 
very  volatile  or  hygroscopic.     Weigh  out  next 
exactly  64  grams  of  cement  and  introduce  into 
the  neck  of  the  flask  by  means  of  a  funnel.   The 
funnel  stem  should  reach  below  the  o  gradua- 
tion on  the  stem,  so  that  should  any  of  the 
cement  fall  against  the  side  of  the  neck  it  will 
be  below  the  space  eventually  occupied  by  the  liquid.    The 
cement  is  added  cautiously  towards  the  last  until  the  para- 


SPECIFIC  GRA  VITY 


123 


ffin  or  benzine  rises  to  the  zero  mark  on 
the  neck  above  the  bulb.  The  remainder 
of  the  cement  is  then  weighed,  and  from 
this  the  quantity  of  cement  which  dis- 
placed 20  cc.  is  calculated  by  difference. 
Instead  of  the  above  method,  the  operator 
may  add  the  entire  64  grams  of  cement. 
The  reading  on  the  neck  plus  20  will  give 
the  number  of  cubic  centimeters  displaced 
by  64  grams  of  cement.  To  find  the  spe- 
cific gravity  in  either  of  the  above  cases 
divide  the  weight  of  the  cement  taken 
by  the  volume  of  liquid  displaced,  the  re- 
sult will  be  the  specific  gravity  of  the  ce- 
ment. The  flask  during  the  operation 
should  be  either  kept  in  a  vessel  of  water 
or  immersed  a  short  while  before  each 
reading  in  order  to  guard  against  errors 
from  variations  in  the  volume  of  benzine 
due  to  temperature. 

Another  form  of  apparatus  in  frequent 
use,  particularly  abroad,  for  taking  the 
specific  gravity  of  cement  is  that  of  Schu- 

With  the  Schu-  ^nnasmodifiedbyCand- 
mann-Candlot  lot  This  Apparatus  (Fig. 
Apparatus.  X9)  consistsof  agraduated 
tube,  B,  terminated  by  a 
bulb,  A.  This  tube  fits  tightly  on  the  - 
flask,  D,  by  means  of  a  ground  joint.  To 


30 


zo 


Fig.  19- 


124 


PHYSICAL  METHODS 


use  the  apparatus,  paraffi-n,  turpentine,  or  benzine  is  in- 
troduced into  the  detached  and  inverted  tube  B  in  suf- 
ficient quantity  to  bring  the  level  of  the  liquid  above 
the  zero  point  on  the  tube  when  the  latter  is  in  position  on 
the  flask  D.  A  note  is  then  made  of  this  point,  the  tube 
is  inverted  and  the  flask  detached.  Into  the  latter  is  then 
introduced  a  known  weight  (usually  100  grams)  of  cement, 
and  the  flask  is  again  connected  with  the  tube.  The  whole 
apparatus  is  now  agitated  to  expel  air  bubbles,  then  set  in 
an  upright  position  and  the  new  height  to  which  the  liquid 
rises  is  read.  The  difference  between  this  height  and  the 
last  is  the  volume  of  liquid  displaced  by  the  cement.  To 
find  the  specjfic  gravity  of  the  cement  divide  the  weight 
of  cement  taken  by  the  volume  displaced,  the  result  will 
be  the  specific  gravity. 

Where  the  apparatus   is   not   at  hand  for   the    above 
methods,  the  specific  gravity  may  be  taken  by  means  of 

the  ordinary  specific  gravity  bottle.  First 
sp  gr  bottle  we^S^  ^e  bottle  empty  then  fill  the  bottle 

with  water  and  weigh,  then  dry  and  fill  with 
benzine  and  weigh.  Calculate  the  specific  gravity  of  ben- 
zine from  the  formula 


where  x  =  sp.  gr.  of  benzine,  B  =  weight  of  bottle  full 
of  benzine,  W  =  weight  of  bottle  full  of  water,  and  p  = 
weight  of  the  empty  bottle. 

Now  introduce  a  weighed  portion  of  the  cement  into  the 


FINENESS  125 

bottle,  fill  with  benzine,  and  weigh.  The  specific  gravity 
of  the  cement  may  then  be  found  by  the  formula 

V  =         C  X  x 

B  +  C  -  D' 

where  B  =  weight  of  the  bottle  full  of  benzine,  C  =  weight 
of  the  cement.  D  =  weight  of  the  bottle  and  the  cement 
and  the  benzine,  x  =  specific  gravity  of  the  cement  as 
found  above,  and  X  =  specific  gravity  of  the  cement.  Tur- 
pentine or  paraffin  may  be  used  in  place  of  benzine. 

FINENESS 

The  fineness  to  which  cement  is  ground  is  an  important 
point.  Since  cement  is  usually  used  with  sand,  the  strength 

of  the  mortar  increases  with  the  fineness  of 
Importance  . 

f  p.  the  cement,  because  the  greater  is  the  cover- 

ing power  of  the  cement,  i.  e. ,  the  more  parts 
of  cement  come  into  action  with  the  sand.  A  test  for  fine- 
ness is  nearly  always  included  in  cement  specifications,  as 
the  indications  from  a  fair  degree  of  fineness  coupled  with 
proper  tensile  strength,  neat,  are  that  the  cement  will  give 
good  results  when  used  with  sand.  The  Committee  on 
Uniform  Cement  Tests  of  the  American  Society  of  Civil  En- 
gineers recommended  in  their  report  that  three  sieves 
should  be  used  in  making  the  fineness  test,  having  2,500, 
5,774,  and  10,000  meshes  per  .square  inch  respectively.  The 
size  wire  used  in  these  sieves  is  very  important  since  it 
regulates  the  size  of  the  opening.  The  2,500  mesh  should 
be  made  of  No.  35,  the  5,774  of  No.  37,  and  the  10,000  of 
No.  40  wire,  Stubbs'  wire  gauge. 


126  PHYSICAL  METHODS 

In  making  this  test,  it  is  usual  to  take  100  grams  and 
after  sifting  until  no  further  appreciable  quantity  can  be 
shaken  or  rapped  through  the  sieve,  weighing 
Makin    the   ^e  res^ue  caugnt  by  the  sieve.     The  weight 
Test  of  this  residue  in  grams  represents  the  per- 

centage of  cement  retained  by  that  particular 
sieve.  It  is  usual  where  the  specifications  call  for  a  test 
with  more  than  one  sieve  to  start  with  the  finest,  and  then 
after  weighing  treat  the  residue  caught  upon  this  with  the 
next  size  in  point  of  coarseness,  etc.,  until  the  coarsest  has 
been  used.  The  metal-framed  sieves  with  top  and  bottom 
are  most  convenient  for  this  test.  They  can  also  be  ob- 
tained in  nests  of  any  desired  size  and  number.  Fig.  20 
shows  a  form  of  mechanical  shaking  sifter,  manufactured 
by  the  Riehl£  Bros.  Testing  Machine  Co.  In  these  nests 
of  sieves  the  coarsest  should  be  at  the  top  and  the  finest 
at  the  bottom.  To  the  weight  of  the  residue  on  each  sieve 
is  to  be  added  the  weight  of  that  caught  on  all  the  sieves 
above  it. 

SETTING  PROPERTIES 

The  rapidity  with  which  a  cement  sets  furnishes  us  with 
no  indication  of  its  strength.  The  test  is  usually  made 
Value  of  to  Determine  the  fitness  of  the  material  for  a 
the  Test.  given  piece  of  work.  For  example,  in  most 
submarine  work  a  quick -setting  cement  is  de- 
sired, that  is,  a  cement  which  loses  its  plasticity  in 
less  than  half  an  hour,  while  for  most  purposes  where 
sufficient  time  will  be  given  the  cement  to  harden  be- 
fore being  brought  into  use,  a  slow-setting  cement  will 


SETTING  PROPERTIES  127 

usually  answer  better,  or  one  that  sets  in  half  an  hour 
or  more.  The  slow-setting  cements  can  be  mixed  in  larger 
quantities  than  the  quick  setting,  and  do  not  have  to  be 


handled  so  quickly,  so  that  for  most  purposes  where  per- 
missible they  are  used. 


128 


PHYSICAL  METHODS 


The  test  proposed  by  General  Gilmore,  U.  S.  A.,  for  de- 
termining setting  properties  is  the  one  most  used  in  this 

country.     It  consists  in  mixing  cakes  of  neat 
Method  of  ,  ,        .      ...  ,     . 

m.  .-        .      cement  from  2  to  3  inches  in  diameter  and  1/2 

Test  inch  thick  to  a  stiff  plastic  consistency  and 

observing  the  time  when  they  will  bear  a 
needle  1/12  inch  in  diameter  weighted  with  1/4  pound. 
This  is  noted  as  the  beginning  of  the  set.  These  pats 
should  be  made  with  a  flat  top  so  as  not  to  catch  the  edge 
of  the  needle.  Trials  are  next 
made  every  now  and  then  with 
a  1/24  inch  in  diameter  needle 
weighted  with  one  pound.  The 
time  at  which  the  cake  is  suffi- 
ciently firm  to  bear  this  latter 
needle  is  noted  as  the  end  of  the 
set.  Fig.  21  shows  the  two  Gil- 
more  wires  or  needles.  It  is  best 
to  have  the  needles  supported  in 
a  rack,  as  shown.  They  will 

[then   bear  perpendicularly  and 

Fig.  21.  evenly  upon  the  top  of  the  pat. 

The  water  with  which  the  pat  is  gauged  should  be  from  60° 
-70°  P.,  and  the  pat  placed  in  air  of  the  same  temperature. 
In  order  to  determine  the  time  of  set  of  slow-setting 
cements  by  the  official  German  method  (cements  which 
Q  set  in  two  hours  or  more  are  called  slow  set- 

Method.         ^n&  ^n  Germany),  take  a  sample  of  neat  ce- 
ment and  mix  for  three  minutes  with  water 


SETTING  PROPERTIES  129 

to  a  stiff  paste  ;  for  quick-setting  cements  only  one  min- 
ute's mixing  is  required.  The  mixture  is  then  spread  on  a 
glass  plate,  at  a  single  operation,  in  the  form  of  a  pat 
i  1/2  cm.  thick  (about  5/8  inch),  and  tapering  towards  the 
edges.  The  consistency  of  the  gauged  cement  should  be 
such  that  a  few  taps  on  the  glass  plate  will  cause  the  mass, 
which  was  placed  thereon  with  a  spatula,  to  flow  outwards 
towards  the  edges.  From  27  to  30  per  cent  of  water  is 
generally  sufficient  for  the  purpose.  When  the  pat  be- 
comes hard  enough  to  withstand  a  slight  pressure  with 
the  finger  nail,  the  cement  may  be  considered  as  set. 

The  above  methods  are  accurate  enough  for  practical  pur- 
poses. 

Where  more  accurate  determinations  for  experimental 
purposes  or  particularly  to  determine  the  beginning  of  the 
set,  as  this  point  is  important  as  determining 
v-  the  time  before  which  the  cement  should  be 

Needle  usec*  since  it  should  not  be  disturbed  after  the 

set  has  begun,  the  Vicat  needle  is  most  used. 
This  is  the  apparatus  adopted  by  the  Association  of  Ger- 
man Cement  Manufacturers  and  also  the  French  Commis- 
sion des  Methodes  d'Essai  des  Materiaux  de  Construction. 
The  Vicat  needle  (Fig.  22)  consists  of  a  frame  K,  in  which 
moves  a  rod,  L.  Over  the  upper  end  of  this  rod  may  be 
slipped  either  of  two  caps,  D  (shown  on  the  needle)  or  A  ; 
and  in  its  lower  end  may  be  fixed,  by  a  thumb-screw,  G, 
either  a  needle,  H,  having  a  cross-section  of  one  square 
millimeter,  or  a  plunger,  B,  i  centimeter  in  diameter.  The 
rod  is  held  in  any  desired  position  in  the  frame  by  the 


130 


PHYSICAL  METHODS 


thumb-screw,  F.  The  rod  carries  an  indicator,  E,  which 
moves  up  and  down  a  scale  on  the  frame  and  shows 
the  position  of  the  rod.  The 
weight  of  the  rod,  L,  with  either 
the  cap,  D,  and  needle,  H,  or  the 
cap,  A,  and  the  rod,  B,  is  300 
grams.  The  paste  of  cement  to 
be  tested  is  held  in  a  rubber  ring 
8  cm.  clear  diameter  and  4  cm. 
high,  resting  on  a  glass  plate,  J. 
The  cement  to  be  tested  is  mixed 
with  water  to  a  plastic  consis- 
tency, and  filled  into  the  rubber 
ring  level  with  the  top.  This  is 
then  immediately  placed  under 
the  rod,  the  latter  having  the 
plunger,  B,  and  cap,  A.  If  the 
plunger  penetrates  the  mortar  to 
a  distance  of  6  mm.  from  the  bot- 
tom ,  the  mortar  is  of  the  proper 
consistency  for  the  test.  The 
needle,  H,  and  cap,  D,  are  now 
Fig.  22.  substituted  for  the  plunger,  B, 

and  cap,  A.  Trials  are  then  made  every  ten  minutes  and  the 
time  when  the  needle  first  refuses  to  entirely  transverse  the 
mortar  in  the  ring  is  noted  as  the  beginning  of  the  set,  while 
the  time  at  which  the  needle  gently  applied  to  the  surface 
of  the  mortar  rests  upon  it  and  does  not  perceptibly  pene- 
trate into  it,  is  said  to  be  the  end  of  the  set. 


TENSILE  STRENGTH  131 

TENSILE   STRENGTH 

While  in  actual  work  cement  is  never  used  in  such  a 
way  as  to  subject  it  to  tensile  stress,  still  the  most  usual 
test  for  cement  is  that  of  the  tensile  strength.  This  test 
is  one  largely  of  convenience.  A  tensile  stress  can  be  more 
easily  applied  and  with  a  less  expensive  machine  than  can 
a  compressive  one,  and  as  the  ratio  between  the  tensile  and 
compressive  strength  of  a  cement  has  been  found  to  be  a 
fairly  constant  one,  the  greater  the  tensile  stress  a  cement 
will  stand  the  greater  in  general  will  be  its  compressive 
strength. 

In  apptying  the  tensile  strength  test  to  a  cement,  bri- 
quettes are  made  of  the  neat  sample,  or  of  any  desired 
proportion  of  cement  and  sand,  by  mixing  with  sufficient 
water  to  form  a  very  stiff  paste  and  then  pressing  into 
moulds,  having  a  definite  cross-section  at  the  middle.  At 
the  expiration  of  a  certain  length  of  time  the  briquettes 
are  pulled  apart  by  means  of  a  machine  designed  for  that 
purpose  and  the  number  of  pounds  stress  required  to  do 
this  is  recorded  as  the  tensile  strength  of  the  cement. 

Fig  23  shows  the  form  of  briquette  recommended  in  the 
report  of  the  committee  on  a  uniform  system  for  tests  of 

cement  of  the  American  Society  of  Civil  Engi- 
Bnquettes.  ,  J  ,  .  ... 

neers,1  which  is  now  the  standard  in  this  coun- 
try, and  Fig.  24,  the  form  recommended  by  the  Association 
of  German  Cement  Makers,  which  is  the  standard  in  Ger- 

1  This  committee  presented  its  report  at  the  annual  meeting  of  the 
society  January  21,  1885,  and  was  then  discharged.  A  new  committee  has 
since  been  appointed,  but  has  as  yet  made  no  report. 


I32 


PHYSICAL  METHODS 


many.  The  dimensions  of  the  two  forms  are  given  in  the 
drawings.  As  will  be  seen,  the  weakest  section  of  briquettes 
of  either  form  is  at  the  center  and  is  one  inch  in  cross-sec- 
tion, in  the  case  of  the  United  States  standard ;  and  5 
square  centimeters  in  that  of  the  German.  Comparative 


Fig.  23. 


Fig.  24. 


tests  show  the  American  standard  to  give  the  higher  re- 
sult of  the  two.  In  the  case  of  briquettes  of  neat  cement, 
this  difference  amounts  sometimes  to  as  much  as  30  or  40 
per  cent  of  the  lower. 

The  briquettes  to  be  broken  at  the  expiration  of  twenty- 
four  hours  are  made  of  neat  cement,  that  is,  cement  alone, 
while  those  to  be  broken  only  after  the  lapse  of  seven  days 
or  longer,  should  be  made  either  of  neat  cement  or  in  the 
case  of  Portland  cements  of  a  mixture  of  one  part  cement 
to  three  parts  sand,  and  in  the  case  of  natural  cements 
of  equal  parts  cement  and  sand. 


TENSILE  STRENGTH 


133 


The  various  kinds  of  molds  used  in  this  country  for 
making  briquettes  are  shown  in  Figs.  25,  26,  and  27.  They 

are  usually  made  of  gun  metal  or  some  allov 
Molds.  ,  ' 

of  copper  that  does  not  easily  rust  on  expo- 
sure to  moisture.  They  are  usually  in  two  pieces  to  facili- 
tate the  removal  of  the  briquette  after  molding.  When 
in  use  the  two  sections  are  held  together  by  means  of  a 


Fig.  25.  Fig.  26.  Fig.  27. 

clamp  provided  with  a  thumb-screw  as  shown  in  Fig.  26, 
or  by  a  spring  as  in  Fig.  27.  Preference  is  usually  to  be 
given  to  the  clamp  rather  than  to  the  spring,  as  the  latter 
is  likely  to  give  a  little  during  the  ramming  of  the  mortar 
into  the  mold,  allowing  the  mold  to  spread,  which  would 


Fig.  28. 

result  in  a  distorted  briquette,  and  an  enlarged  breaking 
section.  Beside  the  single  molds  shown  above,  molds 
are  upon  the  market  holding  more  than  one  briquette. 
Fig.  28  shows  such  a  "gang  mold."  Single  molds  are 
supposed  to  give  higher  results  than  gang  molds. 


i34  PHYSICAL  METHODS 

After  use  the  molds  should  be  wiped  with  a  cloth  and 
a  little  machine  oil.  This  not  only  helps  to  keep  the 
mold,  but  also  to  facilitate  the  subsequent  removal  of  the 
briquette. 

The  sand  recommended  by  the  report  previously  referred 
to  of  the  committee  of  the  American  Society  of  Civil  En- 
gineers, should  be  the  crushed  quartz  used  in 
the  manufacture  of  sand  paper.  As  this 
sand  is  a  commercial  product  it  can  be  obtained  in  large 
quantities  and  of  standard  grades.  The  crushed  quartz 
should  be  of  such  size  that  it  will  all  pass  a  No.  20  sieve 
and  yet  be  retained  upon  a  No.  30. 

Where  the  value  of  the  cement  is  desired  with  regard  to 
some  particular  piece  of  work,  the  sand  used  for  the  test 
may  be  the  sand  that  is  to  be  used  for  the  work.  In  this 
case  it  is  the  mortar  that  is  tested  rather  than  the  cement. 
Just  as  a  series  of  tests  made  with  a  standard  sand  and 
various  brands  of  cement  would  give  the  comparative  value 
of  the  cements,  so  a  series  of  tests  with  an  established 
brand  of  cement  and  various  sands  will  give  the  compara- 
tive value  of  the  sands. 

Two  general  methods  are  employed  for  making  the  mor- 
tar for  the  briquettes :  The  plastic  method  used  in  Eng- 
Maki  h  ^an(^'  France»  and  the  United  States,  and  the 
Briquette  ^r^  method,  which  is  the  standard  method  of 
the  Association  of  German  Cement  Manufac- 
turers. The  dry  method  probably  in  most  cases  gives 
greater  uniformity  of  result  than  the  plastic.  The  latter, 
however,  agrees  more  closely  with  the  conditions  of  the 


TENSILE  STRENGTH  135 

use  of  the  material  in  actual  practice.  The  committee  of 
the  American  Society  of  Civil  Engineers  have  adopted  the 
following  rule  for  making  their  briquettes  : 

' '  The  proportion  of  cement,  sand,  and  water  should  be 
carefully  determined  by  weight,  the  sand  and  the  cement 
mixed  dry,  and  the  water  added  all  at  once.  The  mixing 
must  be  rapid  and  thorough,  and  the  mortar,  which  should 
be  stiff  and  plastic,  should  be  firmly  pressed  into  the 
molds  with  a  trowel,  without  ramming,  and  struck  off 
level  ;  the  mold  in  each  instance  while  being  charged  and 
manipulated  to  be  laid  directly  on  glass,  slate,  or  some 
other  non -absorbing" material. 

"  The  molding  must  be  complete  before  incipient  setting 
begins.  As  soon  as  the  briquettes  are  hard  enough  to 
bear  it,  they  should  be  taken  from  the  molds  and  kept  cov- 
ered with  a  damp  cloth  until  they  are  immersed.  For  the 
sake  of  uniformity,  the  briquettes,  both  of  neat  cement 
and  those  containing  sand,  should  be  immersed  in  water 
at  the  end  of  twenty-four  hours,  except  in  the  case  of  one- 
day  tests. " 

The  Association  of  German  Cement  Manufacturers  have 
adopted  the  following  specification  for  making  the  bri- 
quettes by  hand : 

' '  On  a  metal  or  thick  glass  plate  five  sheets  of  blotting- 
paper  soaked  in  water  are  laid,  and  on  these  are  placed 
five  molds  wetted  with  water.  250  grams  of  cement  and 
75°  grams  of  standard  sand  are  weighed  and  thoroughly 
mixed  dry  in  a  vessel ;  then  100  cc,  of  fresh  water  are 
added  and  the  whole  mass  mixed  for  five  minutes.  With 


i36  PHYSICAL  METHODS 

the  mortar  so  obtained  the  molds  are  at  once  filled,  with 
one  filling  so  high  as  to  be  rounded  on  top,  the  mortar 
being  well  pressed  in.  By  means  of  an  iron  trowel,  5  to  8 
cm.  wide,  35  cm.  long,  and  weighing  about  250  grams, 
the  projecting  mortar  is  pounded,  first  gently  and  from 
the  sides,  then  harder  into  the  molds,  until  the  mortar 
grows  elastic  and  water  flushes  to  the  surface.  A  pound- 
ing of  at  least  one  minute  is  necessary.  An  additional 
filling  and  pounding  of  the  mortar  is  not  admissible,  since 
the  test  pieces  of  the  same  cement  should  have  the  same 
density  at  the  different  testing  stations.  The  mass  is  now 
cut  off  with  a  knife  and  the  surface  smoothed.  The  mold 
is  carefully  taken  off  and  the  test-pieces  placed  in  a  box 
lined  with  zinc,  which  is  to  be  provided  with  a  cover  to 
prevent  a  non-uniform  drying  of  the  test-pieces  at  differ- 
ent temperatures." 

For  making  test-pieces  of  neat  cement : 

' '  The  inside  of  the  molds  are  slightly  oiled,  and  the  same 
are  placed  on  a  metal  or  glass  plate  without  blotting-paper. 
1000  grams  of  cement  are  weighed  out,  200  grams  of  water 
added,  and  the  whole  mass  thoroughly  mixed  for  five 
minutes.  The  forms  are  well  filled  and  then  proceed  as 
for  hand-work  with  sand  mortar." 

The  mortar  for  the  briquettes  should  be  mixed  upon 
some  non-absorbent  substance  such  as  a  slab  of  slate  or  a 
Mixing  the  P^ate  °^  S^ass-  ^  the  plastic  method  is  used, 
Mortar.  "  the  quantity  of  water  used  should  be  just  suf- 
ficient to  make  the  mass  of  about  the  consist- 
ency of  stiff  plasterers '  mortar.  The  proportion  of  water  to 


7  ENSILE  STRENGTH  137 

cement  varies  with  the  fineness,  age,  etc.,  of  the  cement, 
and  also  upon  the  temperature  of  the  air  and  water.  An 
approximate  quantity  for  briquettes  of  neat  Portland  ce- 
ment is  25  per  cent  ;  for  those  of  neat  natural  cement,  30 
per  cent  ;  for  briquettes  of  one  part  sand  and  one  part 
cement,  15  per  cent  ;  and  for  those  of  one  part  cement  and 
three  parts  sand,  12  per  cent  ;  of  the  total  weight  in  either 
case  of  the  sand  and  cement.  The  percentage  of  water 
for  any  given  cement  may  readily  be  found,  by  placing  a 
small  weighed  portion  of  it,  say  100  grams,  upon  the  mix- 
ing slab  and  adding  water  from  a  graduated  cylinder  until 
the  mass  is  of  the  desired  consistency.  Note  is  then  taken 
of  the  quantity  required. 

The  consistency  of  mortar  does  not  depend  entirely  upon 
the  quantity  of  water  used,  but  also  upon  the  manner  and 
the  extent  of  working  the  mortar  in  gauging.  In  the 
French  and  the  German  standard  specification  it  is  re- 
quired that  the  mortar  shall  be  worked  for  five  minutes. 

The  molds  should  be  set  upon  some  level,  smooth,  non- 
absorbent  material  such  as  a  glass  or  slate  slab,  and  the 

molding  must   be  complete  before   incipient 
Hardening  .  ^     ,    . 

the  Bri  setting  begins.     As  soon  as  the  briquettes  are 


quettes  ^ar(^  enougn  to  bear  it  they  should  be  taken 

from  the  molds  and  kept  moist  by  covering 
with  a  damp  cloth  or  placing  in  a  moist  closet  until  they 
are  immersed.  The  moist  closets  are  made  of  tin  or  zinc 
similar  in  shape  to  the  air-bath  described  on  page  18,  and 
are  of  sufficient  size  to  meet  the  requirements  of  the  labora- 
tory in  which  they  are  to  be  used.  The  air  in  them  is  kept 


i38  PHYSICAL  METHODS 

moist  by  a  layer  of  water  upon  the  bottom,  or  by  a  moist 
sponge.  The  briquettes  are  placed  upon  glass  or  metal 
shelves  above  the  surface  of  the  water.  Mr.  Richard  L. 
Humphrey,  in  the  Proceedings  of  the  Engineer's  Club  of 
Philadelphia,  November,  1896,  describes  a  soapstone  moist 
closet  which  he  used  in  the  cement  testing  laboratory  of 
the  city  of  Philadelphia.  For  the  sake  of  uniformity,  the 
briquettes  both  of  neat  cement  and  those  containing  sand 
are  recommended  by  the  committee  of  the  American  Society 
of  Civil  Engineers  to  be  immersed  at  the  end  of  twenty-four 
hours,  except  in  the  case  of  one-day  tests,  where  they  are 
immersed  as  soon  as  set.  Ordinary  fresh  clean  water,  having 
a  temperature  of  from  60°  to  70°  P.,  should  be  used  for  the 
water  of  both  mixing  and  immersion.  The  briquettes 
should  always  be  put  in  the  testing  machine  and  broken 
immediately  after  being  taken  out  of  the  water,  and  the 
temperature  of  the  briquette  and  of  the  testing  room  should 
be  constant,  between  60°  and  70°  F. 

The  briquettes  may  be  placed  in  water  either  flat  or  on 
edge.  The  latter  gives  more  surface  exposed  to  the  water. 
The  tanks  in  which  the  briquettes  are  immersed  may  be 
made  of  galvanized  iron  and  of  any  desired  size.  They 
are  usually,  however,  from  two  to  three  inches  deep.  Where 
space  is  limited,  they  may  be  placed  one  above  the  other 
on  a  suitable  framework. 

The  various  forms  of  clips  are  shown  in  the  following 

illustrations.     Fig.  29   shows  that  recommended  by  the 

CUps  American  Society  of  Civil  Engineers.     This 

latter  form  does  not  seem  to  be  very  satisfac- 


TENSILE  STRENGTH 


139 


tory  as  the  bearing  surface  is  insufficient  and  the  briquette 
is  likely  to  break  from  the  crushing  of  its  surface  at  the 
point  of  contact.  Fig.  30  is  probably  more  to  be  preferred. 
It  affords  sufficient  bearing  surface  without  binding.  Vari- 
ous authorities  at  different  times  have  advocated  cushion- 
ing the  grips  by  placing  blotting  paper  between  jaw  of 
the  grip  and  the  briquette,  or  stretching  rubber  bands 
around  the  jaws,  so  as  to  soften  the  point  of  contact  of 
these  with  the  test  piece.  Mr.  W.  R.  Cock1  has  de- 


Fig.  29. 


Fig.  30. 


vised  the  use  of  a  rubber  bearing  as  shown  in  Fig.  31.  In 
this  clip  the  line  of  contact  between  the  grip  and  the  bri- 
quette is  a  rubber  tube  mounted  on  a  pin.  These  tubes 
are  readily  replaced  for  a  few  cents  when  worn 
out.  Adjustable  and  roller  clips  are  also  upon 
the  market  and  seem  to  give  satisfaction.  In 
order  that  the  stress  upon  the  briquette  shall  be/ 
along  the  proper  lines  great  care  must  be' 
exercised  in  properly  centering  the  briquette 
in  the  clips,  and  the  form  of  the  latter  must 

1  Eng.  News,  Dec.  20,  1890. 


Fig.  31 


I4o  PHYSICAL  METHODS 

be  such  that  it  does  not  clamp  the  head  of  the  briquette 
thus  preventing  the  test  piece  from  adjusting  itself  to  an 
even  bearing.  At  the  same  time  the  surface  of  contact 
must  be  sufficient  to  prevent  the  briquette  from  being 
crushed  at  this  point.  Striking  the  happy  medium  has  so 
far  proved  not  any  too  easy.  The  clips  are  usually  sus- 
pended by  conical  bearings  which  permit  them  to  turn  so 
as  always  to  transmit  the  stress  in  a  direct  line  between 
the  bearings. 

Of  the  various  testing  machines  in  use,  the  Michaelis 

machine  is  almost  universally  used  in  Germany,  while  in 

this  country  the  Fairbanks  (which  is  practi- 

_      .  cally  the  same  as  the  Michaelis)  the  Riehle 

Machine          an(*  t^ie  Olsen  are  most  used. 

The  Michaelis1  double-lever,  automatic  ma- 
chine for  testing  cement  is  described  as  follows:  Upon  a  mas- 
sive pillar,  about  one  foot  in  height,  are  fastened  twolevers, 
connected  with  one  another ;  the  upper  has  a  leverage  of 
10  to  i  and  the  lower  of  5  to  i.  To  the  latter  is  fastened 
the  upper  clip  ;  the  lower  clip  is  attached  by  means  of  a 
ball  point  to  a  screw  with  a  hand  wheel  for  lowering  or 
raising.  There  is  also  a  counter  balance  for  bringing  the 
levers  into  exact  equilibrium.  The  weight  is  applied  by 
means  of  a  stream  of  shot  flowing  into  a  bucket  attached 
to  the  upper  lever.  The  moment  the  specimen  breaks,  the 
bucket  drops  striking  a  lever  below  which  closes  a  trap 
and  shuts  off  the  stream  of  shot  instantly.  The  shot  in 
the  bucket  is  then  weighed  upon  a  spring  or  other  form  of 

1  Gary:  Trans.  Am.  Soc.,  C.  E.,  30,  26. 


TENSILE  STRENGTH  141 

scale.  This  weight,  multiplied  by  10,  gives  the  breaking 
strain  per  centimeter  when  the  German  form  of  briquette 
is  used. 

The  Fairbanks  cement  testing  machine  (Fig.  32)  is  in 


Fig.  32- 

principle  the  same  as  the  Michaelis.  It  differs,  however, 
much  in  form  of  construction.  In  this  machine  the  weight 
of  the  shot  is  determined  on  hanging  the  bucket  on  the 
opposite  end  of  the  lever  used  for  breaking  the  specimen, 
by  means  of  a  sliding  poise.  To  operate  the  machine  : 
Hang  the  cup  F  on  the  end  of  the  beam  D,  as  shown  in 


i42  PHYSICAL  METHODS 

the  illustration.  See  that  the  poise  R  is  at  the  zero  mark, 
and  balance  the  beam  by  turning  the  ball  L. 

Fill  the  hopper  B  with  fine  shot,  place  the  specimen  in 
the  clamps  N  N,  and  adjust  the  hand  wheel  P  so  that  the 
graduated  beam  D  will  rise  to  the  stop  K.  Open  the  auto- 
matic valve  J  so  as  to  allow  the  shot  to  run  slowly  into 
cup  F.  When  the  specimen  breaks,  the  graduated  beam 
D  will  drop  and  automatically  close  the  valve  J. 

If  the  consistency  of  the  cement  is  such  that  the  speci- 
men will  not  break  before  the  beam  strikes  the  valve,  it 
will  be  necessary  to  stop  the  flow  of  shot  and  readjust  the 
hand  wheel.  This  can  best  be  done  by  lifting  the  end  of 
the  beam  against  the  stop  by  hand  and  tightening  the 
hand  wheel  to  hold  the  beam  firmly  in  position.  The  shot 
is  then  to  be  allowed  to  run  until  the  specimen  breaks. 

Remove  the  cup  with  the  shot  in  it,  and  hang  the  coun- 
terpoise weight  G  in  its  place. 

Hang  the  cup  F  on  the  hook  under  the  large  ball  E,  and 
proceed  to  weigh  the  shot  in  the  regular  way,  using  the 
poise  R  on  the  graduated  beam  D,  and  the  weights  H  on 
the  counterpoise  weight  G. 

The  result  will  show  the  number  of  pounds  required  to 
break  the  specimen. 

The  flow  of  shot  can  be  regulated  by  the  cut-off  valve. 

The  Richie"  machine  (Fig.  33)  has  all  the  weight  upon 
one  long  graduated  beam.  The  load  is  applied  to  the 
briquette  by  means  of  the  lower  hand  wheel  which  actu- 
ates a  worm  gear,  while  the  beam  is  kept  in  balance  by  a 
weight  which  is  moved  along  the  beam  on  a  carriage  by 


TENSILE  STRENGTH 


Fig.  33- 

the  upper  hand  wheel.  The  upper  lever  serves  as  an  indi- 
cator. In  testing  a  briquette  both  wheels  must  be  moved 
simultaneously  so  that  the  indicator  vibrates  in  the  center 
of  its  gate.  In  testing  with  this  machine,  the  briquette 
is  placed  in  the  grips,  and,  being  carefully  adjusted,  the 
hand  wheel  connected  to  the  lower  grip,  is  turned  from 


I44  PHYSICAL  METHODS 

left  to  right,  and  continued  until  the  indicator  of  weigh- 
ing beam  (which  moves  in  a  gate  at  the  top  of  the  machine 
and  nearly  on  a  line  with  the  eye  of  the  operator)  drops. 
This  indicator  moves  the  reverse  of  the  weighing  beam, 
and  when  too  much  strain  is  exerted  it  falls,  and  when  too 
much  weight  is  applied  it  raises  to  the  top  of  the  gate.  It 
is  important  that  the  indicator  should  vibrate  in  the  cen- 
ter of  the  gate,  and  rest  neither  up  nor  down.  This  re- 
sult can  be  attained  by  carefully  manipulating  the  large 
hand  wheel  and  the  simultaneous  movement  of  the  poise 
on  the  weighing  beam.  When  the  indicating  beam  drops 
down,  when  the  test  first  begins,  the  rest  of  the  test  can 
usually  continue  without  again  moving  the  large  hand 
wheel,  which  is  shown  underneath  the  end  of  the  shelf.  As 
is  readily  understood,  the  operator  propels  the  poises  back- 
ward and  forward  by  means  of  the  hand  wheel  (at  butt  end 
of  weighing  beam)  and  cord  passing  around  a  pulley  at  the 
other  end  of  the  machine.  By  a  little  practice  a  person 
gets  very  expert,  and  can  make  a  test  with  facility. 

In  the  Olsen  (Fig.  34),  which  is  somewhat  similar  to  the 
Riehle  machine,  the  stress  is  applied  by  means  of  a  hand 
wheel  and  lever,  so  arranged  that  no  torsional  or  trans- 
verse strain  is  imparted  to  the  specimen,  but  a  perfectly 
straight  pull  is  secured. 

The  full  capacity  of  the  machine  is  registered  by  a  poise 
moved  on  a  single  scale  beam,  by  means  of  a  cord  and 
small  hand  wheel  attached  to  the  frame  work  of  the  ma- 
chine, so  the  strain  may  be  applied  and  weighed  evenly 
and  continuously  throughout  the  test.  It  is  also  provided 


TENSILE  STRENGTH 


145 


Pig.  35- 

with  grips  resting  on  pivot  bearings  and  so  adjusted  as  to 
insure  a  perfectly  straight  pull  on  the  specimen. 

Whichever  machine  is  used  the  load  is  to  be  applied  at 
the  rate  of  400  pounds  per  minute. 

None  of  these  machines  are  free  from  sources  of  error. 
In  the  Michaelis  and  the  Fairbanks  machines  there  is  an 


:46  PHYSICAL  METHODS 

error  due  to  the  fact  that  some  time  (in  which  shot  is  fall- 
ing into  the  bucket)  is  taken  by  the  beam  to  fall  to  the 
valve  checking  the  shot  stream  ;  even  then  there  is  a 
stream  of  shot  extending  from  the  valve  opening  to  the 
surface  of  the  shot  in  the  bucket  which  must  fall  into  the 
latter  and  be  weighed  as  part  of  the  load  which  broke  the 
specimen,  though  this  shot  was  not  in  the  bucket  when 
the  specimen  broke.  In  the  other  two  forms  mentioned, 
there  is  an  error  due  to  the  fact  that  the  chain  is  attached 
to  the  poise  at  a  point  not  on  a  line  with  the  knife  edges 
of  the  beam,  giving  the  poise  a  tendency  to  lift  up  or  pull 
down. 

In  cement  testing,  the  personal  equation  enters  very 
largely  into  the  results.     In  a  paper1  by  Prof.  James  Madi- 
son Porter,  of  Lafayette  College,  he  gave 
Lack  of  Uni- 
f       •»    •  a  series  ol  results  upon  the  same  cement 

Tensile  Tests,  ^v  nine  different  operators,  tested  by  the 
method  of  the  Society  of  Civil  Engineers 
as  they  understood  it.  The  results  varied  from  75  to  247 
pounds  per  square  inch.  The  Committee  on  a  Uniform 
System  for  Tests  of  Cement  of  the  American  Society  of 
Civil  Engineers,  in  their  report,  say  : 

' '  The  testing  of  cement  is  not  so  simple  a  process  as  it  is 
thought  to  be.  No  small  degree  of  experience  is  necessary  be- 
fore one  can  manipulate  the  materials  so  as  to  obtain  even  ap- 
proximately accurate  results. 

"The  first  test  of  inexperienced,  though  intelligent  and  care- 
ful persons,  are  usually  very  contradictory  and  inaccurate,  and 
1  Engineering  News,  March  7,  1895. 


TENSILE  STRENGTH  147 

no  amount  of  experience  can  eliminate  the  variations  introduced 
by  the  personal  equations  of  the  most  conscientious  observers. 
Many  things,  apparently  of  minor  importance,  exert  such  a 
marked  influence  upon  the  results,  that  it  is  only  by  the  great- 
est care  in  every  particular,  aided  by  experience  and  intelligence 
that  trustworthy  tests  can  be  made." 

The  personal  equation  probably  plays  its  most  import' 
ant  part  in  the  gauging  of  the  cement,  the  making  of  the 
mortar,  and  the  molding  and  breaking  of  the  briquettes. 
In  order  to  eradicate  these  variations  of  treatment,  ma- 
chines have  been  introduced  upon  the  market  to  do  the 
work  automatically  and  so  do  away  with  whatever 
variations  the  operator  may  introduce  into  the  hand  work, 
principally  among  which  are  ih&  jig  and  the  Faija  mixer, 
and  the  Bohme  hammer. 

The  jig  mixer  in  its  simplest  form  consists  of  an  ordi- 
nary "milk-shake  "  apparatus  (see  Fig.  4,  page 46).  After 
the  proper  proportions  of  water  and  cement 
have  been  ascertained,  sufficient  cement  for 
one  briquette  is  weighed  into  each  cup  and  the  desired 
amount  of  water  poured  upon  it  from  a  graduated  cylinder. 
The  covers  are  then  fastened  down  upon  the  cups  by 
means  of  thumb  screws  and  the  machine  run  for  one  min- 
ute, when  the  mortar  is  ready  for  the  molds.  In  order 
that  the  briquettes  made  from  mortar  mixed  in  this  ma- 
chine shall  be  constant,  it  is  necessary  to  give  each  lot  of 
mortar  the  same  number  of  revolutions  in  the  same  time. 
A  description  of  the  original  and  more  complicated'  jig 
mixer  may  be  found  in  a  paper  upon  the  St.  Louis  Water 


PHYSICAL  METHODS 


The  Faija 
Mixer. 


Works  Cement  Testing  Laboratory,  by  S.  Bent  Russell, 
C.E.,  in  the  Engineering  News,  25,  2. 

The  Faija  mixer  is  the  design  of  the  late  Henry  Faija, 
of  England.     Fig.  36  shows  the  mixer  as  made  by  Riehle 
Bros.  Testing  Machine  Co.,  of  Philadelphia.   It 
consists  of  a  circular  pan  of  about  one  foot  in 
diameter,  within  which  revolve  the  arms  of  a 
stirrer.     These  arms  revolve  around  their  own  axis  in  one 
direction  and  around  the  pan 
in  the  re  verse  direction.   This 
motion   is  given  them  by  a 
fixed  internally  toothed  wheel 
which  actuates  the  pinion  of 
the  stirring  spindle.     To  op- 
erate, first  find  by  means  of 
a  trial   test  by  hand  gauging 
the  proper  proportion  of  water 
to   cement.      Next   place   in 
the  mixer  sufficient  cement  to 
fill  a  gang  of  molds  and  add 

at  once  the  proper  quantity  of  water  for  this  weight  of 
cement.  Then  turn  the  handle  of  the  machine  fairly 
quickly  for  from  a  half  to  three-quarters  of  a  minute,  when 
it  will  be  found  that  the  cement  and  water  are  thoroughly 
mixed  and  ready  for  the  molds.  In  gauging  cement  and 
sand  in  this  machine,  first  mix  the  cement  and  sand  dry 
and  then  add  the  water,  etc. 

The  Bohme  hammer  consists  of  a  tilt  hammer  with  auto- 
matic action.     The  hammer  is  thus  described  by   Max 


TENSILE  STRENGTH  149 

Gary1 :  "  The  hammer  is  driven  by  a  cam  wheel  of  ten 
cams  actuated  by  simple  gearing.  The  wrought-iron 
handle  of  the  hammer  is  let  into  the  cross- 
head  which  carries  the  axle  of  the  hammer 
and  keyed  to  this  cross-head  and  to  the  cap 


The  Bohme 
Hammer. 


1  Trans.  Am.  Soc.  C.E.,  30, 


Fig.  37- 


1 5o  PHYSICAL  METHODS 

so  that  it  may  be  replaced  if  worn.  The  steel  ham- 
mer weighing  4^  pounds,  is  similarly  fastened  to  the 
cap.  As  soon  as  the  intended  number  of  blows  has  been 
delivered,  the  mechanism  is  automatically  checked,  the 
proper  setting  having  been  made  for  this  purpose  before 
beginning  the  work."  (The  number  of  blows  required  in 
the  German  Standard  test  is  150.) 

' '  The  forms  to  receive  the  mortar  consist  of  a  lower  and 
upper  case  held  together  by  springs.  The  lower  case  for 
compression  specimens  consists  of  two  angle  irons  held 
on  a  planed  plate  by  a  grinding  strip  and  a  screw  acting 
on  the  latter.  Upward  motion  is  prevented  by  two  wedge- 
shaped  surfaces.  The  lower  case  and  half  the  upper  one 
is  filled  with  the^mortar  to  be  tested  and  a  plate  laid  upon 
its  surface.  On  this  plate  the  blows  are  delivered.  It  is 
of  vital  importance  that  the  apparatus  rests  upon  a  firm 
non-elastic  foundation;  preferably  it  should  be  placed  and 
fastened  on  a  pier  of  masonry.  " 

Prof.  Charles  D.  Jameson  describes,  in  his  book  on  Port- 
land cement,  a  form  of  machine  in  use  in  his  laboratory  at 

the  University  of  Iowa.     The  main  portion 

The  Jameson        t    ,,  ,  .  .  ,         ,.  ,.     ,       A 

ol   the  machine  consists   ot   a  cylinder  A 

Machine*!  (FiSs-  3§  and   39)  which  is  flanged  at  the 

lower  end,  this  flange  corresponding  in 
shape  and  size  to  the  upper  part  of  the  base.  The  cylinder 
is  bolted  to  the  baseby  four  bolts,  each  bolt  provided  with 
a  filler  that  holds  the  lower  face  of  the  cylinder  i  inch  above 
the  base  plate.  Both  of  these  faces  are  accurately  planed. 
It  is  between  these  two  planed  faces-  that  the  molding 


TENSILE  STRENGTH 


plate  swings,  the  fillers  on  the  bolts  acting  as  stops.  The 
cylinder  is  made  in  two  parts,  bolted  together.  The  bore 
is  the  size  and  shape 
of  the  briquette.  In 
this  bore  works  a 
solid  plunger  of  the 
shape  of  the  bore. 
The  length  of  the 
plunger  is  sufficient 
to  cover  the  feed  hole 
when  at  its  lowest 
point.  The  plunger 
is  connected  to  the 
lever  B  by  the  con- 
necting rod  C.  The 
molding  plate  swings 
in  such  a  manner  that 
when  at  either  ex- 
treme, one  of  the  openings 
is  directly  beneath  the  bore 
of  the  cylinder,  while  the 
other  is  direct- 
ly over  the  ex- 
tractor. These 
extractors  are 
of  the  shape  of 
the  opening  in 
the  molding 
plate  and  are  Fig  39 


Fig.  38. 


i52  PHYSICAL  METHODS 

raised  by  levers.  When  the  extractor  is  at  its  lowest  point 
its  top  is  a  little  below  the  lower  side  of  the  molding  plate. 
The  object  of  the  extractors  is  to  force  the  briquette  from 
the  mold.  On  the  outside  of  the  cylinder  is  the  hopper. 

The  method  of  operation  is  as  follows :  The  piston  is 
raised  until  it  is  above  the  feed  hole,  and  the  cement  or 
mortar  in  the  hopper  is  forced  into  the  cylinder.  The 
molding  plate  is  pushed  against  one  of  the  stops  so  as  to 
bring  one  of  the  openings  under  the  cylinder  bore.  The 
lever  is  forced  down  causing  the  plunger  to  force  the  ce- 
ment or  mortar  into  the  opening  in  the  molding  plate.  The 
molding  plate  is  then  swung  against  the  other  stop.  This 
movement  cuts  off  the  briquette  and  places  it  directly  over 
the  extractor.  The  other  opening  in  the  molding  plate  is 
directly  under  the  cylinder  bore.  The  extractor  is  raised 
by  its  lever,  and  the  briquette  forced  out  and  removed. 
The  extractor  is  lowered,  the  main  plunger  forced  down 
again,  the  molding  plate  swung  and  another  briquette 
made.  The  cylinder  holds  sufficient  mortar  for  three  bri- 
quettes. It  should  then  be  filled  again.  In  the  machine 
as  described  there  is  no  way  of  regulating  the  amount  of 
pressure.  Experiments  made  by  Prof.  Jameson,  however, 
indicate  that  there  is  no  necessity  of  this,  probably  from 
the  fact  that  the  actual  pressure  is  so  great  under  all  cir- 
cumstances that  the  actual  variation  forms  but  a  small 
percentage  of  it,  not  sufficient  to  vary  the  results. 

To  do  away  with  the  personal  equation  in  the  breaking 
of  the  briquette,  Prof.  J.  M.  Porter,  professor  of  civil  en- 
gineering in  Lafayette  College,  has  designed  an  inge- 


TENSILE  STRENGTH 


'S3 


nious  form  of  cement- testing  machine.  In  breaking  a  bri- 
quette with  this  machine,  the  attention  of  the  operator  is 
Porter-Olsen  not  required  after  the  proper  adjustment  of 
Testing  Ma-  the  test-piece  in  the  clips.  He  describes 
chine.  his  machine  as  follows  :' 

The  load  is  applied  by  water  flowing  into  a  tank  suspended 
from  the  long  arm  of  a  very  sensitive  15  to  i  lever.  The  weight 
of  the  lever  and  tank  is  counterbalanced  by  an  adjustable 
weight  on  the  left.  Water  is  admitted  to  the  tank  from 
a  large  reservoir  on  the  roof  under  a  practically  constant  head 
of  90  feet,  so  there  is  no  sensible  variation  of  pressure  in  the 
stream  admitted  through  a  carefully  fitted  gate  valve  in  the 
supply  pipe.  The  position  of  this  valve  at  "on,"  "off,"  and 
all  intermediate  points  is  shown  by  an  index  attached  to  the 
stem  of  the  valve  and  registering  on  a  dial  marked  off  with  the 
number  of  pounds  per  minute  applied  to  the  specimen  as  deter- 
mined and  verified  by  previous  experiment. 

When  the  briquettes  break,  the  lever  drops  a  few  inches,  then 
the  plunger  at  the  right  end  of  the  lever  enters  the  pneumatic 
stop,  and  the  lever  and  tank  are  gradually  brought  to  rest. 
During  the  fall  of  the  tank  and  before  it  comes  to  rest,  a  chain 
attached  to  the  end  of  the  valve  stem  in  the  tank  is  brought 
into  tension  and  arrests  the  descent  of  the  valve  before  its  seat 
stops  descending.  The  opening  of  this  valve  allows  the  con- 
tents of  the  tank  to  be  quickly  discharged  into  a  hopper  placed 
upon  the  floor,  and  is  then  carried  off  through  a  waste  pipe  to 
the  sewer.  As  soon  as  the  tank  has  discharged  its  contents,  the 
weight  on  the  left  end  of  the  lever  brings  the  lever  and  tank 
into  the  position  ,  the  valve  taking  its  seat  during  this  move- 
ment and  the  machine  is  ready  for  another  break.  The  actual 
1  Engineering  News,  March  7,  1895. 


I54  PHYSICAL  METHODS 

load  can  be  applied  at  from  o  to  80  pounds  per  minute,  thus 
giving  an  increase  of  stress  of  from  o  to  1,200  pounds  per  min- 
ute. The  speed  generally  used  is  400  pounds  per  minute,  and 
with  the  valve  set  for  this  speed  the  needle  beam  will  float 
every  time  within  i  second  of  the  proper  time. 

The  stress  on  the  specimen  is  measured  by  a  poise  traveling 
on  a  graduated  scale  beam,  which  can  be  read  by  means  of  a 
vernier  to  i  pound  and  can  be  moved  automatically  or  by  hand 
at  the  wish  of  the  operator.  The  automatic  movement  is  accom- 
plished by  the  following  described  device  : 

The  horizontal  disk  and  its  engaged  friction  wheel  are  driven 
continuously  by  the  pulley  placed  at  the  lower  end  of  the  ver- 
tical shaft  and  belted  to  overhead  shafting.  This  friction  wheel 
is  feathered  to  a  sleeve  that  runs  loose  on  its  shaft  and  carries  a 
coned  clutch  that  is  nominally  disengaged  from  its  cone,  which 
is  also  feathered  to  the  shaft,  and  can  be  moved  slightly  longi- 
tudinally on  the  shaft  into  contact  with  the  clutch  by  the  action 
of  the  vertical  lever. 

When  the  needle  beam  rises,  it  makes  contact  through  a  ver- 
tical pin  in  the  top  of  the  frame,  which  completes  an  electric 
circuit  and  sends  a  current  through  the  electro-magnet  and 
causes  it  to  attract  its  armature  at  the  lower  end  of  the  vertical 
lever,  which,  moving  to  the  right,  engages  the  friction  clutch 
and  causes  the  shaft  to  revolve.  This  shaft  operates  the  sprocket 
wheel  and  chain,  which  draw  out  the  poise  on  the  scale  beam 
until  the  needle  beam  drops,  breaking  the  electric  circuit. 
Breaking  the  electric  circuit  releases  the  armature  and  allows 
the  friction  clutch  to  disengage  and  the  poise  comes  to  rest. 
The  friction  wheel  may  be  set  at  a  greater  or  less  distance  from 
the  center  of  the  disk  by  turning  the  capstan  head  nut,  and  the 
chain  is  overhauled  faster  or  slower,  causing  the  poise  to  move 


SOUNDNESS  155 

accordingly.  If  desired,  the  poise  may  be  operated  by  the  hand 
wheel  without  interfering  with  the  automatic  device  other  than 
cutting  out  the  circuit.  The  chain  is  attached  to  the  poise  in 
line  with  the  three  knife-edges  of  the  scale  beam,  hence  the 
tension  in  the  chain  has  no  tendency  to  lift  up  or  pull  down 
the  poise.  This  point  is  often  overlooked  in  designing  this  de- 
tail, not  only  in  cement  machines,  but  in  testing  machines  in 
general.  The  writer  has  a  cement  machine  in  which  the  error 
due  to  this  cause  is  over  15  pounds. 

SOUNDNESS 

The  most  important  quality  of  cement  is  soundness,  for 
no  watter  how  high  a  degree  of  tensile  strength  a  cement 

may  develop  at  comparatively  short  periods, 
Importance  .,  ; ,  , 

of  the  Test          jt  to  resist  tne  disintegrating  influ- 

ences of  the  atmosphere  or  the  water  in  which 
it  may  be  placed,  it  is  useless  as  a  material  of  construe-, 
tion.  This  tendency  to  disintegrate,  fall  to  a  powder, 
crack  or  expand  on  mixing  the  cement  with  water  is 
termed  "  blowing. "  This  fault  is  usually  due  to  improper 
mixing  of  the  raw  materials  allowing  an  excess  of  lime 
over  what  will  combine  with  the  silica  and  alumina  of  the 
cement  mixture ;  or  an  improper  burning  failing  to  raise 
the  temperature  to  the  point  where  all  the  lime  may  com- 
bine with  the  silica  and  alumina,  thu's  leaving  some  in  the 
uncombined  state.  The  free  lime  on  coming  in  contact 
and  combining  with  the  water  expands  causing  the  cement 
to  crack  and  fall  to  pieces. 

The  soundness  of  cement  is  generally  tested  by  making 
small  pats  or  cakes  of  neat  cement  gauged  with  water  on 


,56  PHYSICAL  METHODS 

glass  plates.  In  size  these  pats  are  */2  inch  thick  at  the 
middle,  tapering  to  a  thin  edge,  and  are  from  3  to  4  inches 
in  diameter.  These  pats  are  placed  in  wa- 
ter and  in  air  and  watched  carefully  for  signs 
of  blowing  such  as  cracks  or  distortion.  The  quantity  of 
water  used  in  gauging  the  cement  is  about  the  same  as  is 
required  in  preparing  the  mortar  for  tensile  strength  bri- 
quettes. Greater  variations,  however,  will  give  more  uni- 
form results  than  would  be  allowable  in  tensile  tests.  The 
cakes  should  be  kept  moist  during  setting  and  until  they 
are  immersed  to  avoid  drying  cracks.  The  test  as  recom- 
mended by  the  Committee  of  the  American  Society  of  Civil 
Engineers  is  as  follows  : 

"  Make  two  cakes  of  neat  cement  two  or  three  inches  in 
diameter,  and  about  one-half  inch  thick,  with  thin  edges. 
Note  the  time  in  minutes  that  these  cakes  when  mixed  with 
water  to  the  consistency  of  stiff  plastic  mortar,  take  to  set 
hard  enough  to  stand  the  wire  test  recommended  by  Gen- 
eral Gilmore,  V3-inch  diameter  wire  loaded  with  */4  °f  a 
pound,  and  '/24  inch  loaded  with  i  pound.  One  of  these 
cakes  when  hard  enough  should  be  put  in  water  and  ex- 
amined from  day  to  day  to  see  if  it  becomes  contorted,  or 
if  cracks  show  themselves  at  the  edges,  such  contortions 
or  cracks  indicating  that  the  cement  is  unfit  for  use  at  that 
time.  In  some  cases  the  tendency  to  crack,  if  due  to  free 
lime,  will  disappear  with  age.  The  remaining  cake  should 
be  kept  in  air  and  its  color  observed,  which  for  a  good  ce- 
ment should  be  uniform  throughout,  yellowish  blotches 
indicating  a  poor  quality,  the  Portland  cements  being  of 


SOUNDNESS  157 

a  bluish  gray  and  the  natural  .cements  being  dark  or  light 
according  to  the  character  of  the  rock  of  which  they  are 
made.  The  color  of  the  cements  when  left  in  air  indicates 
the  quality  much  better  than  when  they  are  put  in  water. " 

The  rules  of  the  Association  of  German  Cement  Manu- 
facturers specify  that  the  test  shall  be  made  as  follows  : 

"  In  carrying  out  this  test,  the  pat  prepared  for  deter- 
mining the  time  of  set  (see  page  128)  should  be  placed  un- 
der water  at  the  end  of  twenty-four  hours,  in  the  case  of 
slow  setting  cements,  but  in  any  case  only  after  it  has  be- 
come set.  This  may  be  done  much  quicker  in  the  case  of 
quick-setting  cements.  The  pats,  especially  in  the  case 
of  slow-setting  cements,  must  be  well  protected  from 
draughts,  and  the  direct  rays  of  the  sun,  until  after  they 
have  become  set.  The  best  method  is  to  place  them  in  a 
closed  box  or  cover  them  with  damp  cloths.  Hair  cracks 
which  are  caused  by  shrinkage,  due  to  rapid  drying,  will 
thus  be  avoided.  These  generally  appear  in  the  center  of 
the  pat  and  are  often  mistaken  by  the  uninitiated  for 
cracks  caused  by  blowing.  If  the  cement  shows  any  crum- 
bling, or  cracks  are  visible  during  the  process  of  harden- 
ing while  under  water,  this  is  a  certain  indication  of  the 
blowing  of  the  cement ;  that  is  to  say,  the  cement  becomes 
cracked  in  consequence  of  an  increase  of  volume  and  a 
gradual  disruption  of  the  particles  previously  connected 
takes  place,  which  11133'  ultimately  lead  to  the  total  de- 
struction of  the  mass.  These  symptoms  of  expansion 
usually  appear  within  three  days,  but  an  observation  ex- 
tending over  twenty-eight  days  is  always  sufficient." 


1 58  PHYSICAL  METHODS 

In  testing  cement  by  the  manner  given  above  it  is  im- 
portant that  the  testing  should  be  continued  over  a  long 

space  of  time.  Many  blowy,  unsound  cements 
Accelerated  .,,  .  '  -  ,  -. 

_  will  not  show  signs  of  cracks  or  distortion 

under  twenty-eight  days,  some  will  not  show 
it  even  at  this  date,  yet  in  time  the  pats  will  fall  to  pieces 
and  ultimately  disintegrate.  Forthis  reason  many  methods 
have  been  proposed  and  tried  for  showing  in  a  shorter 
time  whether  or  not  a  cement  is  reliable  and  fit  to  use.  In 
most  of  these  methods  the  chemical  action  which  causes 
the  blowing  or  expanding,  and  which  is  extended  some- 
times over  a  considerable  period  of  time,  is  hastened  by 
the  aid  of  heat  as  suggested  by  Michaelis  or  by  the  use  of 
chemicals  in  preparing  the  mortar  for  the  pats  as  sug- 
gested by  Candlot,  who  used  calcium  chlorid. 

Probably  the  best  of  the  hot  tests  is  that  of  the  English 
cement  expert,  Henry  Faija.  His  method  consists  in 
Faija's  Test  subJecting  a  freshly  gauged  pat  upon  a  plate 
'  of  glass  prepared  as  directed  above  to  a  moist 
heat  of  100°  to  105°  F.  for  six  or  seven  hours,  or  until 
thoroughly  set,  and  then  immersing  it  in  water  kept  at  a 
temperature  of  115°  to  120°  F.  for  the  remainder  of  the 
twenty-four  hours.  This  treatment  imparts  an  artificial 
age  to  the  cement  and  quickly  brings  out  any  vicious 
qualities  the  cement  may  possess.  For  this  test  he  uses  the 
apparatus  shown  in  Fig.  40.  It  consists  of  a  covered  ves- 
sel in  which  water  is  kept  at  the  even  temperature  of  1 15° 
to  120°  F.  by  means  of  a  water-jacket.  The  inner  vessel 
is  filled  with  water  to  the  height  shown.  Above  the  water- 


SOUNDNESS 


159 


level  is  placed  a  rack.  When  the  water  in  the  inner  ves- 
sel is  at  the  temperature  of 
115°  to  120°  F.  the  upper 
part  of  the  vessel  will  be 
filled  with  aqueous  vapor 
and  this  latter  will  be  at  a 
temperature  of  from  100° 
to  105°  F.  As  soon  as  the 
pat  is  gauged  it  is  put  on 
the  rack  and  left  there  for 
six  hours .  It  is  then  pi aced 
in  the  warm  water  and  al- 
lowed to  remain  eighteen 
hours  longer.  The  author 
of  the  test  states  that  if  a 
test  pat  after  the  above 
treatment  shows  no  signs 
of  cracking  or  blowing  and 
adheres  firmly  to  the  glass 
plate  on  which  it  was  made, 
it  may  be  used  with  perfect 
confidence;  it  will  never 
blow.  This  test  certainly 
seems  fairer  to  the  cement 


Fig.  40. 


than  most  of  the  hot  tests,  many  of  which  would,  if  ap- 
plied to  some  really  good  cements,  cause  them  to  be  rejected. 
Captain  W.  W.  Maclay  modifies  this  test  as  follows  : 
Four  pats  are  prepared  in  the  usual  manner.  One  of  these 
pats  is  placed  in  a  steam-bath  of  a  temperature  of  195° 


160  PHYSICAL  METHODS 

to  200°  F.,   as  soon  as  made.     The  second  pat  is  placed 
in  the  same  bath  as   soon  as  it  will  bear  the  one  pound 
,          wire.     The  third  pat  is  placed  in  the  steam - 
Test  kath   after    double    the   interval  has  passed 

that  took  the  second  pat  to  set  hard,  count- 
ing from  the  time  of  gauging.  The  fourth  pat  is 
placed  in  the  steam-bath  after  twenty-four  hours.  The 
four  pats  are  kept  in  the  steam-bath  three  hours,  when 
they  are  immersed  in  water  at  200°  F.  for  twenty-one  hours 
each,  when  they  are  taken  out  and  examined.  All  four 
pats  after  being  twenty -one  hours  in  hot  water,  should,  to 
pass  the  test  perfectly,  upon  examination  show  no  swell- 
ing, cracks,  nor  distortions,  and  should  adhere  to  the  glass 
plates.  This  latter  requirement,  while  it  obtains  with 
some  cements  nearly  free  from  uncombined  lime,  is  not 
insisted  upon,  the  cracking,  swelling,  and  distortion  being 
the  more  important  features  of  the  test.  Where  the  cement 
is  very  objectionable  from  excess  of  free  lime  the  trouble 
generally  shows  itself  in  the  cracking  or  distortion  of  all 
four  pats.  Where  the  cement  is  not  so  bad,  the  cracking 
and  swelling  takes  place  on  the  first  three  pats  only.  With 
less  objectionable  cement  only  the  first  two  pats  crack  or 
swell  while  the  cracking  and  swelling  of  the  first  pat  can 
generally  be  disregarded. 

Captain  Maclay  does  not  consider  this  test  final,  how- 
ever, but  where  the  cement  fails  to  pass  gives  it  another 
chance  by  testing  briquettes  conserved  in  hot  water  and 
comparing  with  those  kept  in  cold  water.  He  found,  in  a 
general  way,  that  the  average  tensile  strength  of  hot  water 


SOUNDNESS  161 

briquettes  of  pure  cement  four  days  old  are  nearly  as  high 
as  the  normal  seven-day  cold,  while  the  hot  water  seven- 
day  briquettes  require  nearly  the  same  strain  to  pull  them 
apart  as  the  normal  twenty-eight  day  cold,  when  the  ce- 
ment is  of  good  quality.  In  a  poor  cement,  however,  one 
in  which  the  pats  show  distortion  and  cracking,  there  is 
generally  a  marked  falling  off  of  the  hot  water  briquettes 
from  the  above  comparison,  and  one  system  can  be  used 
to  check  the  other.  The  briquettes  are  prepared  at  the 
same  time  the  regular  cold  water  test-pieces  are  made — 
four  additional  sets  of  five  each  for  neat  cement  and  four 
additional  sets  of  mortar.  These  are  allowed  to  set  twenty- 
one  hours  in  moist  air  of  about  60°  F.  They  are  placed 
three  hours  in  the  steam-bath  at  195°  F.  and  then  im- 
mersed in  hot  water  (200°  F.),  after  which  they  are  broken 
when  two,  three,  four,  and  seven  days  old  respectively,  and 
the  breakings  compared  with  the  normal  breakings  of  bri- 
quettes seven  and  twenty-eight  days  old  kept  in  cold  water. 

Dr.  Bohme  suggests  the  kiln  test.  The  Association  of 
German  Cement  Makers  recommend  this  test  as  a  means 
of  quickly  judging  of  the  quality  of  a  cement, 
but  do  not  make  the  test  decisive  and  abide 
by  their  twenty-eight-day  test  on  these  cements  which  fail 
to  pass  the  kiln  test.  Their  method  for  the  test  is  as  fol- 
lows : 

' '  For  making  the  heat  test,  a  stiff  paste  of  neat  cement 
and  water  is  made,  and  from  this  cakes  8  cm.  to  10  cm.  in 
diameter  and  i  cm.  thick  are  formed  on  a  smooth  imper- 
meable plate  covered  with  blotting-paper.  Two  of  these 


1 62  PHYSICAL  METHODS 

cakes  which  are  to  be  protected  against  drying  in  order  to 
prevent  drying  cracks,  are  placed  after  the  lapse  of  twenty- 
four  hours,  or  at  least  only  after  they  have  set,  with  their 
smooth  surface  on  a  metal  plate  and  exposed  for  at  least 
one  hour  to  a  temperature  of  from  110°  C.  to  120°  C.  until 
no  more  water  escapes.  For  this  purpose  the  drying 
closets  in  use  in  chemical  laboratories1  may  be  utilized.  If 
after  this  treatment  the  cakes  show  no  edge  cracks,  the 
cement  is  to  be  considered  in  general  of  constant  volume. 
If  such  cracks  do  appear  the  cement  is  not  to  be  condemned, 
but  the  results  of  the  decisive  test  with  the  cakes  harden- 
ing on  glass  plates  under  water  must  be  waited  for.  It 
must,  however,  be  noticed  that  the  heat  test  does  not  ad- 
mit of  a  final  conclusion  of  the  constancy  of  volume  of 
those  cements  which  contain  more  than  3  per  cent,  of  cal- 
cium sulphate  (gypsum)  or  other  sulphur  combinations." 
Prof.  Tetmajer,  of  Zurich,  modifies  this  method  by 
placing  on  the  bottom  of  the  oven  a  few  millimeters  of 
water.  The  heat  is  gradually  applied  so  as  to  evaporate 
all  the  water  in  from  three  to  six  hours  :  first  that  on  the 
floor  of  the  oven,  and  then  that  absorbed  by  the  mortar. 
The  latter  is  held  on  a  shelf  above  the  floor.  The  temper- 
ature of  the  oven  remains  at  about  95°  C.  until  the  water 
is  entirely  evaporated.  After  this  the  heating  is  con- 
tinued half  an  hour  longer  in  such  a  manner  as  to  raise 
the  temperature  of  the  oven  to  120°  C.  This  will  bring 
the  temperature  of  the  interior  of  the  briquette  at  a  little 
over  100°  C.  It  is  difficult  to  obtain  comparative  results 

1  See  page  18. 


SOUNDNESS  163 

by  this  method  as  the  heat  is  not  the  same  for  all  speci- 
mens, since  after  the  evaporation  of  the  water,  the  heat  is 
much  greater  at  the  bottom  than  at  the  top  of  the  oven. 

This  test,  also  devised  by  Prof.  Tetmajer,  is  very  simi- 
lar to  the  one  just  given.  It  consists  in  rolling  a  ball  of 
_  mortar  and  then  flattening  the  ball  to  the  thick- 

Test  ness  of  half  an  inch.  The  consistency  of  the 

mortar  should  be  such  that  it  shall  neither 
crack  in  flattening  nor  run  at  the  edges.  These  pats  are 
placed  in  a  vessel  of  cold  water  immediately  after  gauging 
and  heat  applied  and  regulated  so  that  the  water  boils  in 
about  an  hour.  The  boiling  is  continued  for  three  hours, 
when  the  pats  are  removed  and  examined  for  checking  and 
cracking. 

Candlot  discovered  by  a  series  of  experiments  upon  ce- 
ment that  if  the  cement  is  either  gauged  with  or  kept  in 
.  water  containing  calcium  chlorid  the  free  lime 

Chi  'd  *n  ^  *s  slaked  much  more  quickly.  The  more 
Test  concentrated  the  solution  the  more  marked 

the  effect.  The  action  of  the  salt  is,  there- 
fore, similar  to  that  of  heat,  to  increase  the  chemical  action 
causing  expansion.  If  the  cement  is  gauged  with  a  con- 
centrated solution  of  calcium  chlorid,  the  lime  will  proba- 
bly all  be  slaked  before  the  cement  sets,  so  that  no  crack- 
ing will  occur  on  hardening,  even  if  much  free  lime  is 
present.  If,  however,  the  calcium  chlorid  solution  is  more 
dilute  (40  grams  to  the  liter)  it  will  only  cause  slaking  of 
a  very  small  percentage  of  the  free  lime,  such  a  small  per- 
centage as  is  unobjectionable  in  cements.  If  a  pat 


1 64 


PHYSICAL  METHODS 


Bauschinger's 
Calipers. 


made  of  this  mortar  is  then  kept  in  a  calcium  chlorid  so- 
lution of  the  same  strength,  the  slaking  of  the  rest  of  the 
lime  will  be  greatly  hastened  and  cracking  will  soon  ap- 
pear if  a  harmful  quantity  of  free  lime  is  present.  To 
carry  out  the  test,  gauge  the  cement  with  a  4  per  cent  so- 
lution (40  grams  to  the  liter)  of  calcium  chlorid,  make  into 
pats  upon  glass  plates  and  allow  to  set,  after  which  im- 
merse the  pats  in  the  cold  4  per  cent  solution  of  calcium 
chlorid  for  twenty-four  hours  and  then  remove  and  exam- 
ine for  cracks,  softening,  etc. 

The  expansion  or  contraction 
of  cement  during  hardening  may 
be  measured  di- 
rectly   and  very 
accurately   by 
means  of   Baushinger's   caliper 
apparatus  (Fig.  41).     By  means 
of  this   instrument   changes  in 
the  length  of  small  parallel  opipe- 
dons,  100  mm.  long 
and  5  sq.  cm.  cross 
section,  maybeaccu- 
rately    measured    to 
within    1/200    mm. 
The  apparatus   con- 
sists  of  a  stirrup- 
shaped  caliper,  hav- 
ing a  fine  micrometer 
screw  on  its  right  arm,  the  left  being  the  support  of  a 


Fig.  4 


SOUNDNESS  165 

sensitive  lever.  The  shorter  arm  of  this  lever  terminates 
in  a  blunt  caliper  point  and  is  pressed  against  the  meas- 
uring screw  by  a  spring  attached  to  the  long  arm.  The 
calipers  are  readily  moved  in  any  direction  and  the  mi- 
crometer is  read  in  the  usual  manner.  One  revolution  of 
the  screw  equals  0.5  mm.  and  the  readings  on  the  head 
are  made  at  1/200  mm.  The  specimen  is  molded  with 
square  cavities  in  the  end,  and  in  these  are  set  plates  of 
glass  containing  centers  for  the  caliper  points.  The  mold- 
ing is  done  similar  to  that  for  tension  specimens  except 
that  both  sides  should  be  repeatedly  struck  off  smooth.  It 
requires  but  a  few  minutes  to  measure  a  specimen  by  this 
apparatus. 


THE  DETECTION   OF  ADULTERATION 
IN  PORTLAND  CEMENT 


Cements  are  adulterated  with  hydraulic  lime,  blast-fur- 
nace slag,  ground  limestone,  shale,  ashes,  etc.  Some  of 
these  substances  are  so  similar  to  Portland  cement  that 
chemical  analysis  fails  to  show  their  presence.  It  is, 
therefore,  necessary  to  direct  special  tests  to  their  de- 
tection. When  present  in  small  quantities,  it  is  probable 
that  even  such  tests  will  fail  to  show  positively  an  adul- 
terated cement. 

Drs.  R.  and  W.  Fresenius,1  at  the  request  of  the  Asso- 
ciation of  German  Cement  Manufacturers,  made  investi- 
gations into  the  subject   of  cement  adul- 
Tests  of  Drs. 
R  and  W  teration  looking  to  a  method  of  detecting 

Fresenius.  t^ie  same-  They  experimented  upon  twelve 

samples  of  pure  Portland  cement  from  Ger- 
many, England,  and  France,  and  compared  the  results  of 
tests  upon  these  with  the  results  obtained  by  similar  tests 
upon  three  kinds  of  hydraulic  lime,  three  kinds  of  weath- 
ered slag,  and  two  of  ground  slag.  The  cements  were  of 
various  ages  and  had  been  exposed  to  the  air  for  various 
lengths  of  time.  Below  are  tabulated  their  experiments 
for  comparison. 

1  Ztschr.  anal.  Chem.,  33,  175,  and  34,  66. 


A  D  UL  TERA  TION  IN  FOR  TLA  ND  CEMENT         167 


! 

2 

3 

4 

5 

Alkalini- 

Description. 

Speci- 
ic  gra- 
vity. 

I<oss  on 
igni- 
tion. 

ty  im- 
paited  to 
water  by 
0.5  gram. 
cc.  of  de- 

Volume 
of  nor- 
mal acid 
neutral- 
ized by  i 

Weight 
of 
KMnO.. 
reduced 
by  i 

Weight 
ofC02 
absorbed 

bys 

Per 

cinormal 

gram. 

gram. 

grams. 

cent. 

P  acid. 

Portland  cement  A 

3-155 

1-58 

6.25 

cc, 

20.71 

mg. 
0.79 

mg. 

1.4 

B 

3-125 

2-59 

4.62 

21.50 

2.38 

1.6 

C 

3-155 

2.  1  1 

4-50 

20.28 

0-93 

1.8 

"                "         D 

3-144 

1.98 

5-io 

21.67 

1.  12 

I.O 

E 

3-144 

1-25 

6.12 

19.60 

0.98 

1.6 

"          F 

3-134 

2.04 

4-95 

20.72 

1.  21 

i.i 

G 

3-144 

0.71 

4-30 

22.20 

0.89 

o.o 

H 

3-125 

I.  II 

4-29 

20.30 

1.07 

0.7 

J 

3-134 

I.OO 

4.00 

19.40 

2.01 

0.0 

"         K 

3-144 

0-34 

4.21 

20.70 

0.98 

0.0 

I, 

3-154 

1.49 

4.60 

18.80 

2.80 

0.3 

M 

3-125 

1-25 

5-50 

20.70 

2-33 

0.0 

Hydraulic  lime      A 

2.441 

18.26 

20.23 

21-35 

1.40 

27.8 

"               "         B 

2-551 

17.82 

22.73 

26.80 

0-93 

31.3 

C 

2.520 

19.60 

19.72 

19.96 

0.98 

47-7 

Weathered  slag      A 

3.012 

0.76 

0.91 

14.19 

74.60 

3-6 

B 

3-003 

1.92 

0.70 

13.67 

60.67 

3-5 

C 

2.967 

i.  ii 

I.OO 

9.70 

44-34 

2-9 

Ground  slag             I 

3-003 

0.32 

-.0.31 

3-6o 

64.40 

2-4 

"         "              II 

2-873 

0-43. 

•>.  .  I 

8.20 

73-27 

2.2 

As  the  result   of  these  experiments  they  proposed  the 
following  tests  for  the  detectioa  of  adulteration  : 

Proposed        l-  ThesPecific  gravity. 

Tests  This  must  not  be  lower  than  3.10. 

2.  The  loss  on  ignition. 

This  should  be  between  0.3  and  2. 59  per  cent ;  certainly 
not  much  more. 


168  DE  TECTION  OF  ADUL  TERA  TION 

3.  The  alkalinity  imparted  to  water.    0.5  gram  of  ce- 
ment should  not  render  50  cc.  of  water  so  alkaline  as  to 
require  more  than  6.25  cc.  nor  less  than  4  cc.  of  decinor- 
mal  acid  to  neutralize. 

4.  The  volume  of  normal  acid  neutralized. 

One  gram  of  cement  should  neutralize  from  18.8  to  21.7 
cc.  of  normal  acid. 

5.  The  volume  of  potassium  permanganate  reduced. 
One  gram  of  cement  should  reduce  not  much  more  than 

0.0028  gram  of  potassium  permanganate. 

6.  The  weight  of  carbon  dioxid  absorbed. 

Three  grams  of  cement  should  not  absorb  more  than 
0.0018  gram  of  carbon  dioxid. 

The  tests  i,  3,  4,  and  5  are  for  the  detection  of  slag  and 
i,  2,  3,  and  6  for  the  detection  of  hydraulic  lime. 

Drs.  R.  and  W.  Fresenius  also  tried  these  tests  upon  ex- 
perimental mixtures  containing  10  per  cent  of  slag  or  hy- 
draulic lime,  and  in  each  case  were  able  to  detect  the  im- 
purity. 

The  methods  employed  for  carrying  out  the  tests  were 
as  follows : 

.  i .  They  used  for  taking  the  specific  gravity 

Out  the          ^e  met^°^  °f  Schuman  (see  page  123),  with 
Tests  turpentine  as  the  liquid.    The  end  of  the  tube 

was  corked  to  prevent  evaporation,  the  tem- 
perature kept  constant,  and  the  vessel  carefully  shaken  to 
displace  air  bubbles. 

2.  For  loss  on  ignition  2  grams  of  cement  were  weighed 
into  a  tared  crucible,  and  then  heated  over  a  Bunsen  burner 


IN  PORTLAND  CEMENT  169 

for  twenty  minutes.     The  loss  shown  on  again  weighing 
was  the  loss  on  ignition. 

3.  For  the  "  alkalinity  to  water  test."     The  substance 
was  finely  powdered  and  passed  through  a  sieve  of  5,000 
meshes  to  the  square  centimeter.1     Of  the  resulting  pow- 
der, i  gram  was  shaken  up  with  100  cc.  of  distilled  water 
without  warming  for  ten  minutes.     The  solution  was  then 
passed  through  a  dry  filter-paper  into  a  dry  vessel  and 
50  cc.  of  the  filtrate  titrated  with  decinormal  hydrochloric 
acid.2 

4.  For  " standard  acid  necessary  to  decompose."     One 
gram  of  the  fine  powder  obtained  in  3  was  shaken  with 
30  cc.  of  normal  hydrochloric  acid3  and  70  cc.  of  water  for 
ten  minutes,  without  warming,  and  filtered  through  a  dry 
filter-paper,  50  cc.  of  the  filtrate  were  then  titrated  with 
normal  caustic  soda.4 

5.  For  the  volume  of  permanganate  reduced.     One  gram 
of  the  fine  powder,  obtained  in  3,  was  treated  with  a  mix- 

1  32,260  meshes  to  the  square  inch. 

2  To   make  decinormal  hydrochloric  acid,  refer  to  page  84  with  the 
notes  under  this  section,  and  taking  such  a  quantity  of  dilute  hydrochloric 
acid  as  contains  3.65  grams  of  HC1,  dilute  this  volume  to   i  liter.    Check 
its  value  by  one  of  the  methods  given  in  the  section  referred  to.    The  2/6  N 
nitric  acid  may  be  diluted  to  Vio  N  strength  and  used  in   place  of  the  Vio  N 
hydrochloric  acid. 

3  Normal  acid  should  contain  36.5  grams  of  HC1  per  liter. 

4  To  prepare  normal  caustic  soda,  refer  to  page  87,  and  using  the  above 
normal  acid  as  a  standard  proceed  as  directed  there.    The  2/6  N  solutions 
used  in  checking  the  per  cent  of  lime  in  cement  mixture  (see  page  83)  may 
be  used  for  this  test.    lu  this  case  shake  up  the  cement  with  a   mixtui  e  of 
75  cc.  of  2/5  normal    acid  and  25  cc.  of  water,  and  titrate  back  with   the  2/6 
normal  alkali. 


iyo  DETECTION  OF  ADULTERA  TION 

ture  of  50  cc.  of  dilute  sulfuric  acid  (sp.  gr.  1.12)  and  100 
cc.  of  water.  The  resulting  solution  was  then  titrated 
with  potassium  permanganate  solution.1 

6.  For  carbon  dioxid  absorbed,  about  3  grams  of  the 
fine  powder  obtained  as  in  3,  were  placed  in  a  weighed 
tube  and  a  stream  of  carbon  dioxid  allowed  to  pass  over 
it.  The  sample  was  then  dried  in  a  desiccator  over  sul- 
furic acid  (sp.  gr.  1.84)  and  weighed.  The  increase  in 
weight  gave  the  amount  of  carbon  dioxid  absorbed,  a  small 
calcium  chlorid  drying  tube  was  placed  after  the  tube  con- 
taining the  cement  to  absorb  any  water  evolved. 

L,e  Chatelier  has  devised  a  very  neat  test  for  the  adulter- 
ation in  cement,  depending  upon  the  lower  density  of  the 
adulterant  than  of  the  cement.  His  method 
..  C ,  Jfte~  consists  in  separating  these  lighter  impurities 
from  the  cement  by  means  of  a  heavy  liquid, 
a  mixture  of  methyl  iodid  and  benzene,  prepared  of  such 
strength  that  they  float  upon  its  surface  while  the  pure 
Portland  sinks  to  the  bottom. 

As  the  first  step  the  methyl  iodid  solution  must  be  pre- 
pared. This  should  be  of  density  2.95  according  to  L,e 

,    Chatelier.     As  the  density'  of  the  methyl 
Preparation  of     .  .       ... 

»u    H     v  iodid  itseli   is  3.1,  benzene  must  be  added 

Liquid.  *n  sma^  quantities  until  a  crystal  of  ara- 

gonite  (serving  as  a  guide)  whose  density 

is  2.94  just  remains  at  the  surface.  Since  very  small  quan- 

i  Dissolve  0.28  gram  of  KMnO4  in  100  cc.  of  water.  Not  much  more 
than  i  cc.  of  this  solution,  or  2  cc.  of  the  solution  used  to  determine  ferric 
oxid  in  cement  (page  53)  should  be  required  if  the  cement  is  unadulterated. 


IN  PORTLAND  CEMENT  171 

tities  of  benzene  change  the  density  of  the  methyl  iodid 
considerably  it  is  well  to  make  two  solutions,  one  a  little 
above  and  one  a  little  below  the  density  sought,  and  then 
to  add  the  one  to  the  other  until  the  required  density  is 
obtained.  By  this  means  a  more  gradual  change  is  affected 
and  the  danger  of  overrunning  themark  is  lessened.  Q 

Le  Chatelier  used  in  his  experiments  a  little 
glass  tube  10  mm.  in  diameter  and  70  mm.  long. 
The  tube  (Fig.  42)  is  widened  at  the  top  to  a  fun- 
Apparatus  ne^  anc*  drawn  at  tne  bottom  with  a 
regular  slope  to  an  opening  of  i  mm. 
diameter.  This  opening  is  closed  on  the  interior 
a  little  above  the  bottom  by  a  plunger  consisting 
of  a  small  emery  ground-glass  stopper  on  the  end 
of  a  glass  rod,  which  projects  above  the  funnel  top.  i  ¥ 

To  make  a  test  the  stopper  is  wet  with  water  to  .  " 
make  a  tight  joint  and  inserted  into  the  opening 
of  the  tube.  Grease  cannot  be  used  as  it  is  dissolved  by 
the  methyl  iodid  solution.  Ten  grams  of  the  suspected 
cement  are  weighed  into  the  tube  and  5  cc.  of 
methyl  iodid  solution  (sp.  gr.  2.95),  prepared  as 
above,  poured  upon  it.  A  thin  platinum  wire  bent  into  aloop 
around  the  plunger  is  then  moved  around  and  up  and  down 
in  the  liquid  in  a  lively  manner  in  order  to  drive  out  all 
air  bubbles  and  mix  the  cement  and  liquid  thoroughly. 
The  apparatus  is  now  set  aside  for  an  hour,  when  it  will 
be  found  that  the  slag  is  on  top  and  the  cement  below. 
The  apparatus  is  now  placed  over  a  dry  filter,  the  stopper 
raised  and  the  cement  and  part  of  the  liquid  allowed  to 


I72  DE TECTION  OF  ADUL  TERA  TION 

run  out.  The  cement  is  retained  upon  the  filter  while  the 
liquid  is  caught  in  a  vessel  below  and  may  be  used  again. 
The  slag  and  the  rest  of  the  liquid  are  then  run  out  upon 
another  filter,  and  the  excess  of  liquid  caught  in  a  vessel 
for  use  again.  The  filters  containing  the  slag  and  cement 
are  washed  with  benzene,  dried  and  weighed  separately. 
From  the  weights  the  percentage  of  adulteration  can  be 
calculated.  The  slag  and  cement  can  then  be  analyzed 
chemically,  if  thought  necessary,  as  a  further  guide. 

The  microscope  furnishes  us  with  a  very  good  means  of 
detecting  added  material  in  cement.     Butler1  recommends 

that  those  particles  which  pass  a  76  sieve  and 
Microscopic  ' 

Test  are  retained  upon   a   1 20  sieve  be  examined 

with  a  low  power  (say  a  one-inch)  objective. 
The  particles  of  pure,  well-burned  cement  clinker  of  this 
size  will  then  appear  dark,  almost  black  in  color,  resem- 
bling coke  somewhat,  and  will  possess  the  characteristic 
spongy  honey-combed  appearance  of  cement  clinker.  The 
particles  of  less  well-burned  clinker,  always  present  in  ce- 
ment, will,  when  examined  in  the  same  way,  present  the 
same  shape  and  structure,  but  will  differ  in  color,  being 
light  brown  and  semitransparent,  resembling  gum  arable. 
Intermediate  products  range  from  black  to  light  brown. 
These  particles  are  always  of  a  more  or  less  rounded  na- 
ture. Particles  of  slag  of  the  same  size  viewed  under  the 
same  conditions  differ  somewhat  in  color,  according  to  the 
nature  of  the  slag.  Usually  the  particles  are  light  colored 
of  angular  fracture,  and  instead  of  the  particles  presenting 

1  "  Portland  Cement,"  p.  273. 


IN  PORTLAND  CEMENT  173 

a  rounded  appearance  the  edges  are  sharp  like  flint.  Not 
to  be  mistaken  for  the  slag,  however,  are  the  particles  of 
debris  from  the  millstones  used  to  grind  the  clinker.  These 
latter  may  be  distinguished  from  the  slag  by  picking  out 
the  particles  in  question  with  a  pair  of  pincers,  crushing 
them  in  a  small  agate  mortar  and  treating  them  with  hy- 
drochloric acid.  The  slag  is  readily  attacked  while  the 
debris  from  the  millstones  is  not  attacked.  Particles  of 
iron  from  the  crusher  are  also  present  in  the  residue  caught 
upon  the  120  sieve.  These  may  be  identified  by  their 
black  metallic  appearance  and  their  behavior  with  the 
magnet.  Unburned  coke  is  present  when  coal  or  coke  has 
been  used  in  burning  the  cement.  This  may  be  readily 
distinguished  by  its  brilliant  black  color  and  by  picking 
out  the  black  particles  with  a  pair  of  tweezers  and  heating 
on  platinum  foil,  when  the  coke  will,  of  course,  burn  to 
an  ash. 


APPENDIX 


Tables 

i.    TABU*  OF  THE  ATOMIC  WEIGHTS  OF  THE  MORE  IMPORTANT 
ELEMENTS.    O  =  i 


Name. 

Symbol 

Weight 

Name. 

Symbol 

Weight 

Al 
Sb 
As 
Ba 
Bi 
B 
Br 
Cd 
Ca 
C 
Cl 
Cr 
Co 
Cu 
F 
Au 
H 
I 

27.1 
I2O.4 
75-0 
137-4 
208.1 

II.O 

80.0 
112.4 
40.1 

12.0 

35-5 
52.1 

63-6 
19.1 
197.2 

I.O 

126.9 

Fe 
Pb 
Mg 
Mn 
Hg 
Ni 
N 
0 
P 
P 
K 
Si 
Ag 
Na 
Sr 
S 
Sn 
Zn 

56.0 
206.9 
24.1 
55-0 
2OO.O 
58.7 
14.0 

16.0 
31.0 
194.9 

28.4 
107.9 
23.1 
87.6 
32.1 
119.1 
65-4 

Lead  

Magnesium   
Manganese  

. 

. 

Nickel          .    ..   . 

g 

Phosphorus   

Chlorin  .   .  . 

a  mum 

o  assmm 

Cobalt  

con 

d^ 

Gold  .  . 

Hydrogen  

Tin  . 

lodin  

Zinc  .         ... 

TABLES 


175 


TABLE  OF  FACTORS 


Found. 

Sought. 

Factor. 

Found. 

Sought. 

Factor. 

CdS  

CaS 

Me  P  O,  •  • 

MeO 

CaSO  

CaO 

Me  P,O,  •• 

MeCO 

CaSO 

CaCO 

K  PtCl 

Ko 

CaS  

CaSO 

I  8872 

K  PtCl  •  •  • 

KC1 

CO 

Q 

NaCl 

Na  O 

CO 

CaCO 

BaSO 

CO 

MfCO 

BaSO 

SO 

Ag-Cl 

HC1 

BaSO 

&u$ 
H  SO 

Fe 

Fe  O 

I  4284 

BaSO 

n2ou4 
CaSO 

o  ^8^6^ 

Fe  O    . 

Fe 

BaSO 

CaS 

0.70007 

176 


TABLES 

uS  VO     r»  00      Q     **     W 


•  »-<          T- 

O*    O*    »•-      >-.     N      ?f  <N      rO- 

d    6   066666666 


Tj-LOiO^vO 

666666 


f>  r-H  M    u->  O 


o?    8    «    w"'ft^-?irto?l0o'2'^^-Io 


ddddo'ddddddddddddd' 


d   d   o   6   d    6    6    d    6    6    d   *6   *6    d 


666666666666 


O"-«(NrOrJ-vOl^OO 

ddo"dddd"dd>ddVdd? 


h^GO     O      —     N      fOTf\O     t^-OO^^o'M^r')? 
N  M     C?MVfOl^'M      tOC7s(r)Gl0     N^      ° 

d    d   d    d    d    d    d    o"    d    d    d    d    d    o-    d 


. 

0    'O-oo    oivo    o    -^-06    N    r'w    uoror-M    10 

O     O     O     H-ip-jC4w     (N     rOrOTf-«J--^ioiO^OvO     r^ 

oooooooooddooo'do'dd 


°  6  6  6 

o3S  3 

111  I 

o  M  M  M 


ial  i 

2^6^ 

2  rf  !- 


si! 


TABLES 


177 


8  8< 

I! 


3  w  S 
3  3  w 


1  1  4  II  8  5  § 


PPPPPPPPPPP   |    o 


o  p  p  p  p  p  p  p  p  p  p 


f  IIISIIIII  1 


pppppppppp 


w   !  ppppppppppp 

S       -3><«^"oo"w8v'ow5c«v^ 


o    o   p   o   p   p    p    p   p   p 

Illlllgfil 


SPECIFIC  GRAVITIES  OF  NITRIC  ACID. 


Specific 
gravities 

at^C. 

II 

PH 

loo  parts  by 
weight  contain 

i  liter  contains 
kilograms  of 

Correction 
of  sp.  gr. 
for±i°C. 

N206. 

HN03 

N206. 

HN03. 

.00 

0 

o 

0.08 

O.IO 

O.OOI 

O.OOI 

O.OOOI 

.01 

1.4 

2 

1.62 

1.90 

0.016 

0.019 

O.OOOI 

.02 

2-7 

4 

3-17 

3-70 

0.033 

0.038 

O.OOOI 

.03 

4-1 

6 

4.71 

5-50 

0.049 

0.057 

0.0002 

-04 

5-4 

8 

6.22 

7.26 

0.064 

0.075 

0.0002 

•"5 

6-7 

o 

7.71 

8.99 

0.081 

0.094 

O  OOO2 

.06 

8.0 

2 

9-15 

10.68 

0.097 

0.113 

O.0003 

.07 

9-4 

4 

10.57 

12.33 

0.113 

0.132 

0.0003 

.08 

10.6 

6 

11.96 

13-95 

0.129 

0.151 

0.0004 

.09 

11.9 

8 

15-53 

0.145 

0.169 

0.0004 

.10 

13.0 

20 

I4-67 

17.11 

0.161 

o.  188 

O.OO04 

.11 

14.2 

22 

16.00 

18.67 

0.177 

0.207 

O.OOO5 

.12 
•13 

lii 

2 

38 

20.23 

21.77 

0-195 

0.2II 

0.227 
0.246 

0.0005 
0.0005 

•M 

i?-? 

28 

19.98 

23.31 

0.228 

0.266 

0.0006 

3 

18.8 
19.8 

30 

21.29 
22.60 

24.84 
26.36 

0.245 
0.262 

0.286 
0.306 

0.0006 
0.0006 

-17 

20.9 

34 

2390 

27.88 

0.279 

0.326 

O.OOO7 

.18 

22.0 

36 

25.18 

29.38 

0.297 

0-347 

O.O007 

•19 

23-0 

38 

26.47 

30.88 

0.315 

0.367 

O.O007 

.20 

24.0  ,  ' 

40 

27.74 

32-36 

0-333 

0.388 

O.OOO7 

.21 

25.0 

42 

28.99 

33-82 

0-351 

0.409 

O.OOOS 

.22 

26.0 

30.24 

0.369 

0.430 

0.0008 

•23 

26.9 

46 

31-53 

36.78 

0.387 

0.452 

o.oooS 

.24 

27.9 

48 

32.82 

38.29 

0.407 

0.475 

0.0008 

50 

34-13 

39.82 

0.427 

0.498 

0.0009 

•2? 

29.7 
30.6 

52 

54 

35-44 
36-75 

42:87 

0-447 
0.467 

0.521 

0.544 

0.0009 
0.0009 

.28 

31-5 

56 

38.07 

44.41 

0.487 

0.568 

0.0009 

.29 
•30 

32-4 

33-3 

g 

39-39 
40.71 

45-95 
47-49 

0.508 
0.529 

0.593 
0.617 

O.OOIO 
O.OOIO 

•31 

34-2 

62 

42.06 

49.07 

0-551 

0.643 

O.OOIO 

•32 

35-o 

64 

43-47 

50.71 

0-573 

0.669 

O.OOII 

•33 

35-8 

66 

44-89 

52.37 

°-597 

0.697 

O.OOII 

•34 

36.6 

68 

46.35 

54-07 

0.621 

0.725 

O.OOII 

•35 

37-4 

70 

47.82 

55-79 

0.645 

0-753 

O.OOII 

•36 

38.2 

72 

49-35 

57-57 

0.671 

0.783 

O.OOI  2 

•37 

39-o 

74 

50.91 

59-39 

0.698 

0.814 

0.0013 

.38 

39-8 

76 

52.52 

61.27 

0.725 

0.846 

0.0013 

•39 

40-5 

78 

54-20 

63-23 

0-753 

0.879 

0.0013 

.40 

41.2 

80 

55-97 

65.3° 

0.783 

0.914 

0.0013 

.41 

42.0 

82 

57-86 

67.50 

0.816 

0.952 

0.0014 

.42 

42-7 

84 

59.83 

69.80 

0.849 

0.991 

0.0014 

•43 

43-4- 

86 

61.86 

72.17 

0.885 

1.032 

0.0014 

•44 

44.1 

88 

64.01 

74.68 

0.921 

1-075 

0.0015 

•45 

44.8 

00 

66.24 

77.28 

0.961 

1.  121 

0.0015 

.46 

45-4 

92 

68.56 

79.98 

1.  001 

I.I68 

0.0015 

"$ 

g 

8 

71.06 
73-76 

82.90 
86.05 

1.045 
1.092 

I.2I9 
1.274 

0.0015 
0.0015 

•49 

47-4 

98 

76.80 

89.60 

1.144 

1-335 

o  0015 

•50 

48.1 

IOO 

80.65 

94.09 

I.2IO 

1.411 

0.0016 

•51 

48.7 

102 

84.09 

98.10 

1.270 

1.481 

0.0017 

1-52 

49-4 

104 

85.44 

99.67 

1.299 

I-5I5 

0.0017 

INDEX 


Adulteration  of  Portland  cement 166 

detection  of 166 

Alkalies,  determination  of  in  cement 78,    80 

mixture 104 

day 78 

limestone 112 

slurry 104 

in  Portland  cement 12 

Alumina,  determination  of  in  cement 20,  24,  27,  29,    31 

mixture 101 

clay 114,  115 

limestone 106,  no,  112 

slurry 101 

in  Portland  cement 10 

American  Portland  cements,  analyses  of 2 

Analytical  methods 15 

Analyses  of  Portland  cements,  table  of 2 

Appendix 174 

Atomic  weights,  table  of 175 

Bauschinger's  calipers 164 

Belgian  Portland  cement,  analyses  of  .  : 2 

Blowing  in  cements,  tests  for " 155 

cause  of 8,  155 

Bohme  hammer 147,  148 

Boiling  test  for  soundness  of  cement 163 

Briquettes,  forms  of,  for  tensile  tests 131 

making  for  tensile  tests 134 

machines 149 

Calcimeter,  Scheibler's 94 

Calcium  carbonate,  rapid  determination  of,  in  cement  mixture  .   .   .83,    94 

chlorid,  test  for  soundness  of  cement 163 

sulfid,  determination  of  in  cement     61 

volumetric,  determination  of 4° 

Candlot's  test  for  soundness  of  cement 163 


:8o  INDEX 

Carbon  dioxid,  determination  of,  in  cement 64,  73,    76 

mixture 104 

clay 64 

limestone 112 

slurry 94,  104 

in  Portland  cement 13 

Cement  mixture,  analysis  of 82,  94,    99 

rapid  methods  for  estimating  lime  in 83,    94 

Clay,  analysis  of 113 

Clips,  forms  used  for  holding  briquettes 138 

Cock  clip 139 

Combined  water,  determination  of,  in  cement 64 

mixture 104 

clay 120 

limestone 112 

slurry 104 

Composition  of  Portland  cement 1-14 

Contraction  of  Portland  cement.    See  expansion  etc. 

Decomposition  of  Portland  cement  by  water 4 

acids 20 

Definition  of  Portland  cement I 

Drying  ovens 18,  19 

samples 17 

English  Portland  cement,  analyses  of 2 

Expansion  in  cement*,  cause  of 8,  155 

measurement  of 164 

tests  for 155 

Factors,  table  of 175 

Faija  mixer 147,  148 

's  test  for  soundness 158 

Fairbanks  machine  for  tensile  strength  tests 141 

Ferric  oxid,  determination  of  in  cement 20,  24,  27,  29,  31,  49,  53 

mixture 101 

clay 114,  115 

limestone 106,  no,  112 

slurry 101 

in  Portland  cement 10 

Fineness  of  cement,  importance  of 125 

test  of 125 

French  Portland  cement,  analyses  of 2 


INDEX  181 

Fresenius,  Drs.  R.  and  W.,  tests  of,  for  adulteration 166 

German  Portland  cements,  analyses  of 2 

Gilmore's  needles  for  testing  set 128 

Gooch  crucible 39 

Grappiers'  Tiel,  analysis  of 4 

Grinding  samples 16 

Hardening  briquettes  for  tensile  tests 137 

of  Portland  cement,  theory  of 4 

Hydraulic  index 5,      7 

Insoluble  silicious  matter,  determination  of,  in  limestone 109,  112 

Iron  pyrites  in  clay,  determination  of 121 

Jameson  briquette  machine 150 

Jig  mixer 147 

Kiln  test  for  soundness  of  cement 161 

I,e  Chatelier's  apparatus  for  taking  sp  gr.  of  cement 122 

test  for  adulteration  in  cement 170 

theories  and  researches 3,  4,      5 

I<ime,  determination  of,  in  cement 20,  25,  27,  29,  32,  40,    48 

mixture 102 

clay 116 

limestone 107,  no,  112 

slurry 102 

in  Portland  cement 8 

Limestone,  analysis  of 105 

Load,  rate  of  application  in-breaking  briquettes 145 

I,oss  on  ignition,  determination  of,  in  cement 78,  168 

clay 120 

limestone 112 

Machines  for  tensile  tests 140 

Maclay's  test  for  soundness 160 

Magnesia,  determination  of,  in  cement 20,  25,  27,  30,  32,    42 

mixture 103 

clay 116 

limestone 108,  no,  112 

slurry 103 

in  Portland  cement 11 

volumetric  determination  of 42 

Mechanical  shaker 46,    47 

Michaelis  machine  for  tensile  strength  tests 140 

Microscopic  test  for  adulterations  in  Portland  cement 172 


i82  INDEX 

Mixers  for  cement  mortar 147,  148 

Moisture,  determination  of,  in  cement,  etc .      18 

Mortar  for  briquettes,  pats,  etc.,  mixing  of 136 

Molds  for  making  briquettes 133 

Natural  cements,  table  of  analyses  of 14 

Nature  of  Portland  cement I 

Newberry's  formula  for  hydraulic  index 7 

Nitric  acid,  table  of  the  specific  gravities  of 178 

Olsen  machine  for  tensile  strength  tests 144 

Organic  matter,  determination  of,  in  limestone in 

Physical  methods 112 

Porter-Olsen  machine  for  tensile  strength  tests 152 

Potassium  bichromate,  standard,  preparation  of 49 

permanganate,  standard  for  ferric  oxid,  preparation  of  ...     53 
calcium  ...     40 

Reductor,  Shimer's 55 

Riehle  machine  for  tensile  strength  tests 142 

Sample,  preparation  of,  for  analysis 15 

Sampling  Portland  cement 15 

Sand,  test  of,  for  use  with  cement 1:4 

used  in  making  tensile  strength  tests 134 

Scheibler's  calcimeter 94 

Schumann-Caiidlot's  apparatus  for  taking  sp.  gr.  of  cement 123 

Setting  properties  of  cement,  test  of 126 

Shimer's  crucible  for  CO2  and  H2O  determinations 64,    73 

reductor 55 

Silica,  determination  of,  in  cement 20,  23,  26,  28,  31,    48 

mixture 100,  103 

day 113 

limestone 105,  109 

slurry 100,  103 

Silica,  free,  hydrated  and  combined  in  clay,  determination  of  .   .   .118,  119 

Slurry,  analysis  of 82,    99 

Sodium  arsenate,  preparation  of  standard  solution  of 43 

thiosulfate,        "  "  "  43 

Soundness,  tests  for 155,  158 

Specific  gravity,  determination  of 122 

Standard  acid,  preparation  of 84,  87,    93 

alkali,         "  " 83,  87,    93 

Strength  of  Portland  cement,  test  of  tensile 131 


INDEX  183 

Substances  found  in  cement 7 

Sulfuric  acid,  determination  of,  in  cement 59,  60 

mixture 104 

clay 121 

limestone 112 

slurry 104 

Sulfur  in  Portland  cement 12 

Tables 2,  14,  98,  174,  175,  176,  177,  178 

Tensile  strength  of  cement,  test  of    .   ..." 131 

Testing  machines  for  tensile  strength 140 

Tetmajer's  tests  for  soundness  of  cement     162 

Tiel  Grappiers 3 

Uniformity  in  cement  testing,  lack  of .  146 

methods  of  securing 147 

Vicat  needle  for  testing  set  of  cements              129 

Water,  combined,  determination  of,  in  cement 64 

mixture 104 

clay 120 

limestone 112 

slurry 104 


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